c#.net_unit_3_4_5
(Unit-III)
Working with ADO.net
Introduction:
Microsoft ActiveX Data Objects.NET (ADO.NET) is a model used
by .NET applications using which you can communicate with the database directly
for retrieving and manipulating data.
ADO.NET is the main
data access system that .NET application uses. ADO.NET uses a disconnected data
architecture, which means that the data you work with is just a copy of the
data in the database.
New Features in
ADO.NET
The new features of ADO.NET are as follows:
Ø
Language-Integrated
Query (LINQ): LINQ is a new innovation and one of the components of .NET
Framework 3.5 that adds native data capabilities to .NET languages using syntax
similar to SQL. LINQ to ADO.NET is a LINQ technology to enable querying in
ADO.NET using LINQ programming model. LINQ to ADO.NET consists of two related
technologies: LINQ to DataSet and LINQ to SQL. LINQ to DataSet provides faster
querying of data on the contents of a DataSet. LINQ to SQL enables you to directly
query SQL Server databases.
Ø
LINQ to
DataSet: LINQ to DataSet provides LINQ capabilities for disconnected data
stored in dataset. LINQ to DataSet makes it easier and faster to query over
data cached in a DataSet object. The LINQ to DataSet feature enables you to
work more productively.
Ø
LINQ to
SQL: LINQ to SQL is a component of .NET 3.5 Framework that provides a
run-time infrastructure for managing relational data as objects. You can use
LINQ to SQL technology for translating a query into a SQL query, and then issue
it against tables in a SQL Server database. LINQ to SQL supports all the key
capabilities that you would expect while working with SQL. You can inset,
update, and delete the information from the table.
Explain Components of
ADO.Net
ADO.NET contains a set of classes that expose data access
services. It provides a rich set of components for creating distributed
applications. ADO.NET uses a logical process flow containing components.
The two main components of ADO.NET for accessing and manipulating
data are data provider and dataset. The data provider contains the Connection, Command, DataReader,
and DataAdapter objects. The connection object provides connectivity
to the database. The Command object
provides access to database commands for retrieving and manipulating data in a
database. The DataReader object retrieves data from the database in a
read-only, forward-only mode. The
DataAdapter object uses Command objects
to execute SQL commands. The DataAdapter loads
the DataSet object with data
and also resolves changes that were made to the data in the DataSet object back to the database.
Data Providers
The data provider contains the following four main objects:
Ø
Connection:
Establishes connection with the database. The base class for all the Connection objects is the DbConnection class. The Connection objects have the methods for
opening and closing connection. The .NET framework provides two types of
Connection objects: the SqlConnection
object, which is designed specifically to connect to Microsoft SQL Server and
the OleDbConnetion object, which is
designed to provide connections to a wide range of databases, such as Microsoft
Access and Oracle.
Ø
Command:
Executes a command against the database and retrieves a DataReader or DataSet. It
also executes the INSERT, UPDATE, or DELETE command against the database. The
base class for all Command objects
is the DbCommand class. The Command object is represented by two
classes: SqlCommand and OleDbCommand. The Command object provides three methods that are used to execute
commands on the database. The ExecuteNonQuery()
method executes the commands that have no return value such as INSERT, UPDATE,
or DELETE. The ExecuteScalar()
method returns a single value from a database query. The ExecuteReader() method returns a result set by way of the DataReader objet
Ø
DataReader:
Retrieves data from the database in a forward-only, read-only mode. The
base class for all DataReader
objects is the DbDataReader class.
The DataReader object is returned as a result of calling the
ExecuteReader() method of the Command object.
Ø
DataAdapter:
retrieves data from the database and stores data in a dataset and reflects
the changes made in the dataset to the database. The base class for all DataAdapter objects is the DbDataAdapter class. The DataAdapter object acts as intermediary
for all the communication between the database and DataSet object. The DataAdapter
object is used to fill a DataTable or DataSet objects with data from the
database using the Fill() method. The DataAdapter object commits the changes to
the database by calling the Update() method.
Datasets
The
other major component of ADO.NET is the DataSet object. The DataSet object
always remains disconnected from the database. Consequently reducing load on
the database. The DataAdapter object is used to connect a dataset to a data
provider. The DataAdapter object is used as an intermediary between the dataset
and the data provider.
Q.Explain Basic Operations in ADO.NET
BASIC OPERATIONS IN
ADO.NET
·
Creating a Connection to a Database
·
Executing Commands by using Command object
·
Adding and Configuring a Data Adapter
·
Creating a Data Set
·
Using Data Adapter to retrieve data in a Data
Set
v
Creating
a Connection to a Database
For
working with the data from a database, you need to first establish a connection
with the database.
Using the Wizard
You can create a connection string for any data provider
using the wizard. Here you can see a simple example to connect to the Northwind database.
1.
Open Microsoft Visual Studio 2008 from Startà All Programsà Microsoft Visual
Studio 2008à
Microsoft Visual Studio 2008.
2.
Select Fileà
New à
Project. The New Project dialog box appears.
3.
In the New Project dialog box, select Visual C#
under the Project types pane and Windows Forms Application from the Templates
pane.
4.
Enter the name for the application as
DatabaseOperationsExample and also provide a location for the application.
5.
Click the OK button to create a
DatabaseOperationsExample application.
6.
Select Viewà
Server Explorer to open the Server Explorer window.
7.
Right-click the Data Connections option from the
Server Explorer window and select the Add Connection option from the context
menu.
The Add Connection dialog box appears from
where you can select the type of data source you want to attach to your application.
8.
Click the Change button to select the data
source for your application. The Change Data Source dialog box appears from
where you can select the data source.
9.
Select Microsoft SQL Server as the data source
to connect to a SQL Server database.
10.
Click the OK button. The Add Connection dialog
box reappears with the Microsoft SQL Server (SqlClient) option selected as a
data source.
11.
Select the server name from the Server name
drop-down list.
By default, the radio button beside the
Use Windows Authentication option is selected. If you want to use SQL Server authentication,
then click the radio button beside the Use SQL Server Authentication option,
and provide user name and password for authentication.
12.
Now, select the database or enter the name of
the database you want to connect to in the Select or enter a database name
drop-down list.
13.
Click the
Test Connection button. A message box appears with the message Test Connection
succeeded.
14.
Click the
OK button of the message box.
15.
Now,
click the OK button of the Add Connection dialog box. You will notice tht the
data source is added to your application in the Server Explorer.
Using a Connection String
Use
the ConnectionString property of the OleDbConnection class, for SQL Server, use
the ConnectionString property of the SqlConnection class, and for an Oracle
data source, use the ConnectionString property of the OracleConnection class.
In
the SQL Server connection string, the parameters are discussed as follows:
Ø
Data
Source: Represents the name or the network address of the SQL Server
instance to which you need to connect.
Ø
Initial
Catalog: Represents the name of the database.
Ø
Integrated
Security: Accepts two Boolean values either True or False. If the value is
True then the current Windows account credentials are used for authentication.
The default value is True.
Next,
let’s see how to execute commands by using the Command object.
v
Using a
Command Object
The command object is one of the basic components of ADO .NET.
- The Command Object uses the connection object to
execute SQL queries.
- The queries can be in the Form of Inline text, Stored
Procedures or direct Table access.
- An important feature of Command object is that it can
be used to execute queries and Stored Procedures with Parameters.
- If a select query is issued, the result set it returns
is usually stored in either a DataSet or a DataReader object.
Now, Let us have a
look at various Execute Methods that can be called from a Command Object.
|
Property |
Description |
|
ExecuteNonQuery |
This method executes the command specifies and returns the
number of rows affected. |
|
ExecuteReader |
The ExecuteReader method executes the command specified and
returns an instance of SqlDataReader class. |
|
ExecuteScalar |
This method executes the command specified and returns the
first column of first row of the result set. The remaining rows and column
are ignored. |
EX:
ExecuteNonQuery
1.
The ExecuteNonQuery
method is used to execute the command and return the number of rows affected.
2.
The ExecuteNonQuery
method cannot be used to return the result set.
string connectionString =
@"server=localhost;userid=user1;password=12345;database=mydb";
MySqlConnection connection = null;
try
{
connection = new MySqlConnection(connectionString);
connection.Open();
MySqlCommand cmd = new MySqlCommand();
cmd.Connection =
connection;
cmd.CommandText =
"INSERT INTO Customers(Name) VALUES(@Name)";
cmd.Prepare();
cmd.Parameters.AddWithValue("@Name",
"Bill Gates");
cmd.ExecuteNonQuery();
}
finally
{
if (connection
!= null)
connection.Close();
}
v
Adding
and Configuring a Data Adapter
1. A
data adapter enables you to access data from a database in a disconnected way.
Let’s now learn how we can access data in a data adapter from a database by
performing the following steps:
In the DatabaseOperationsExample application, set the Text
property to Form1 to Basic Database Operations.
2. Right-click
the Data tab of the Toolbox and select the Choose Items option from the context
menu that appears.
The choose Toolbox Items dialog box
appears.
3. Under
the .NET Framework Components tab in the Choose Toolbox Items dialog box, click
the check box beside the SqlDataAdapter option.
4. Then
click the OK button to close the Choose Toolbox Items dialog box. The Choose
Toolbox Items dialog box closes and the SqlDataAdapter control is added to the
Toolbox.
5. Now,
drag and drop a SqlDataAdapter control to the form. The Data Adapter
Configuration Wizard appears.
6. Select
the existing connection from the Which data connection should the data adapter
use? Drop-down list or create a new connection by clicking the New Connection
button. Clicking the New Connection button opens the Add Connection dialog box.
7. Click
the Next button. The next page appears for Data Adapter Configuration Wizard,
which prompts the user to select a command type.
The page displays the following three options
to select:
Ø
Use SQL
statements: select this option to allow the data adapter use a SQL
statement to populate a table in a dataset. This option is by default selected.
Ø
Create
new stored procedures: Select this option to create a new stored procedure
to read and update a table from the database.
Ø
Use
existing stored procedures: Select this option to allow the data adapter to
use an existing stored to read and update a table from the database.
In
this case, we will go with the first option that is the Use SQL statements option.
8. Click
the Next button. The next page appears for the Data Adapter Configuration
Wizard which prompts the user to generate an SQL statement.
9. Now,
either create a SQL statement or select the existing stored procedures. For
building a SQL statement, click the Query
Builder button. The Query Builder dialog box appears along with a Add Table
dialog box.
10. Select
the table, for example Employees
from the Add Table dialog box.
11. Click the Add button to add the Employees
table to the Query Builder.
12. Now
click the close button to close the Add Table. The Employees table is added to
the Query Builder dialog box.
At the top of the Query Builder dialog box,
you can see all the fields of the Employees table either you can select some
fields or all the fields from the table.
13. Select
the check box beside the *(All Columns) option
from the Employees table.
14. Click
the OK button to create the SQL statement. You can see that the SQL statement
appears in the Data Adapter
Configuration Wizard.
15. Click
the Next button. Data Adapter Configuration Wizard appears with the information
of successful configuration of the data adapter.
16. Click
the Finish button to close the Data
Adapter Configuration Wizard. You can see a data adapter, sqlDataAdapter1 and a connection object, sqlConnection1 appears on
the Component Tray.
17. Now
select Dataà
Preview Data to preview the data from the data adapter.
The Preview Data
dialog box appears.
18. Click
the Preview button to view the data from the database in the Results pane.
19. Finally,
click the close button to close the Preview Data dialog box.
v
Creating
a Dataset
Datasets as already explained, contains a cached copy of the tables
of as database. The dataset is independent of the database and so the
interaction with existing databases is controlled through the data adapter. You
can fill data in a dataset by using the Fill() method of the data adapter.
Now,
let’s create a dataset by performing the following steps:
1. Open
the DatabaseOpearationsExample application
2. Select
Dataà
Generate Dataset.
The
Generate dataset dialog box appears, which prompts the user to select a
dataset.
You
can select an existing dataset or create a new one. By default, the new radio
button is selected. You can provide a name for the new dataset or you can use
the existing default name as DataSet1. The generate Dataset dialog box also
prompts the user to select a table to add to the dataset. By default the table
Employees is selected.
3. Now,
click the Ok button to add the dataset to the application. The dataset, dataset11, is added to the Component
Tray.
Using a Data Adapter to Retrieve Data in a
Dataset
So far, we have created a data adapter and a
dataset. Let’s now see how to display data on a DataGridView control using
data adapter and dataset. To do so, perform the following steps:
1.
Open the DatabaseOperationsExample
application.
2.
Drag and drop a DataGridView control from the
Data tab of the Toolbox to the form. A smart tag appears.
3.
Select a data source, for example, DataSet1 from
the Choose Data Source drop-down list.
The dataSet11BindingSource
binding source is added to the Component Tray.
4.
Now, again select the Choose Data Source drop-down list and select the Employees table.
The employeesBindingSource
binding source is added to the Component Tray.
5.
Resize the form to accommodate the data of the Employees table.
6.
Import the System.Data.SqlClient
namespace by using the using
statement as shown in the following code snippet:
Using
System.Data.SqlClient;
7.
Add the code snippet as listed in the Load event of the form to display
employee details on a DataGridView
control.
Private void
Form1_Load(object sender, EventArgs e)
{
sqlDataAdapter1.Fill(dataset11);
}
The Fill() method is used to populate the dataset dataSett11
with employees details.
8.
Press the F5 key to execute the
DatabaseOperationsExample application.
Explain the types of Data Binding in
Windows Forms
Data binding means to bind controls to display
data sources. Data binding can be used to bind either a particular field in a
table or bind the entire table to a control.
There
are two types of data binding in Windows forms:
·
Simple
data binding
·
Complex
data binding.
Simple Data Binding
Simple data binding allows you to display one data element,
such as a field’s value from a table on a control in Visual Basic, you can
simple bind any property of a control to a data value.
For example, you can bind a Text property of a TextBox
control, Size and image properties of a PictureBox control or the BackColor
property of a Label control to a data source. You can bind a property of a
control to a data source by using the DataBindings property of the control.
In simple terms, you can say that simple data binding is the
ability of a control to bind a single data element.
Let’s see an example of simple data binding. For that, perform
the following steps:
1. Create
an application named WindowsFormsDataBinding.
2. Set
the Text property of Form1 to Simple
Data Binding.
3. Drag
and drop the controls n Form1 and also set the values for the respective
properties of the controls.
4. Import
the System.data.SqlClient namespace by using the using statement.
using System.Data.SqlClient;
5. Now
add the code in the Load event of Form1 to display the details of the
employee whose EmployeeID is 6:
private void Form1_Load(object sender, EventArgs e)
{
SqlConnection con;
con = new SqlConnection(“Data
Source=SUMITA-PC\\SQLEXPRESS;Initial
Catalog=northwnd; Integrated Security=True”);
con.Open();
DataSet ds= new DataSet();
SqlDataAdapter da = new SqlDataAdapter(“Select * from
Employees where Employee=6”, con);
da.Fill(ds, “Employees”);
textBox1.DataBindings.Add(“Text”, ds, “Employees.EmployeeId”);
textBox2.DataBindings.Add(“Text”, ds, “Employees.LastName”);
textBox3.DataBindings.Add(“Text”, ds, “Employees.FirstName”);
textBox4.DataBindings.Add(“Text”, ds, “Employees.Title”);
}
6. Press
the F5 key to execute the WindowsFormsDataBinding application .
Complex Data Binding
Complex data binding enables binding of a
control o more than one data element, such as more than one record in a
database. Some of the controls that support complex data binding are
DataGridView, ComboBox, ListBox, and CheckedListBox controls. Complex data
binding can be performed using the following properties:
Ø
DataSource:
Represents the data source, typically a dataset, such as dataSet11.
Ø
DataMember:
Represents the data member you want to work with, in the data source, typically
a table in a dataset, such as the Customers table in the NorthWind database.
DataGridView control uses this property to determine which table to display.
Ø
DisplayMember:
Represents the field you want a control to display, such as the customer’s id, CustomerID. ListBox control uses the DisplayMember and ValueMember properties instead of a DataMember property for data binding.
Ø
ValueMember:
Represents the field you want the control to return in properties, such as
returning the customer ID by using the SelectedValue
property. The ListBox control uses the DisplayMember
and ValueMember properties, instead
of a DataMember property.
let’s
see an example of complex data binding through code. For that, perform the
following steps:
1.
Open the application named
WindowsFormsDataBinding.
2.
Right-click the WindowsFormsDataBinding
application in the Solution Explorer and select Add à Windows Forms from the
context menu to add a new form to the application.
The Add New Item dialog box appears.
3.
Click the Add button to add Form2 to the
application.
4.
Set the Text property to Form2 to Complex Data
Binding.
5.
Resize the form to accommodate all employee
details.
6.
Drag and drop a DataGridView control from the
Data tab of the Toolbox to the form.
7.
Import the System.Data.SqlClient namespace by
using the using statement.
using System.Data.SqlClient;
8.
Now add the code in the Load event of Form2 to
display the details of all employees in a data grid view:
private void
Form2_Load(object sender, EventArgs e)
{
SqlConnection con;
con = new SqlConnection(“Data
Source=SUMITA-PC\\SQLEXPRESS;Initial
Catalog=northwnd; Integrated Security=True”);
con.Open();
DataSet ds= new DataSet();
SqlDataAdapter da = new SqlDataAdapter(“Select * from
Employees”, con);
da.Fill(ds, “Employees”);
dataGridView1.DataSource=ds;
dataGridView1.Datamember=”Employees”;
}
The DataSource property is used to bind a DataGridView control with the data source
and the DataMember property is used
to set the table name from which the employee details need to be displayed.
9.
Set the start up form to Form2.
10.
Press the F5 key to execute the
WindowsFormsDataBinding application.
UNIT –IV
What
is LINQ?
LINQ (Language Integrated
Query) is uniform query syntax in C# and VB.NET to retrieve data from different
sources and formats.
For example, SQL is a Structured Query Language used to save and
retrieve data from a database. In the same way, LINQ is a structured query
syntax built in C# and VB.NET to retrieve data from different types of data
sources such as collections, ADO.Net DataSet, XML Docs, web service and MS SQL
Server and other databases.
Q. Explain Executing Simple LINQ Query.
·
A simple LINQ query is executed in a foreach
statement.
·
The foreach statement in c# requires the
IEnumerable or IEnumerable<T> interface.
·
A linq query contains three clauses: from ,where and select
Perform the following
steps:
1. Click
start->all programs->Microsoft visual studio 2008-> to open the visual
studio 2008 IDE
2. In
the Visual Studio 2008 IDE, select File->new-> project
3. In the new project dialog box, select
visual c#->windows in the project types pane and the windows form
application option in the template pane
4. Enter LinqQUERY in the name text box to
specify the name of the application, and enter an appropriate location for the
application in the location box.
5. Click
the ok button .linqQUERY application is created.
6. Add
a listview control and a button control to Form1 and change the Text property
of button1 to Click.
7. double
click on button ,and add the code
int[] numbers=new
int[7]{0,1,2,3,4,5,6};
var numquery=from num in
numbers where (num%2)==0
select num;
foreach(int num in numquery)
{
Listview1.Items.Add(num.Tostring());
}
8. press
the F5 key to run the application
Q. Standard query operators in LINQ:
|
Operator Type |
Description |
|
Sorting |
Changing the order of a sequence returned by a
query |
|
Set |
Returns a result set in the form of a collection
based on the presence or absence of elements |
|
Filtering |
Restricts the result set to contain the elements
that satisfy a specific condition |
|
Projection |
Transforms an object into different type of new
object |
|
Partition |
Divides the input sequence into two sections,
without rearranging the elements and returns one section |
|
Grouping |
Puts the data into groups such that elements in
each group share a common attribute. |
|
Join |
Joins two data sources with objects that share a
common attribute in both the data sources. |
|
Aggregate |
Computes a single value from a collection |
|
Zip |
Combines two collections into one. |
Sorting Operators
Sorting operators in LINQ arrange the elements of a sequence
based on one or more attributes, it means that to use the sorting operator you
first need to specify a particular attribute and perform primary sorting on the
elements. The sorting operators are
|
Clauses |
Description |
|
OrderBy |
Sorts a set of elements in ascending order |
|
OrderByDescending |
Sorts a set of elements in descending order |
|
ThenBy |
Perform a secondary sort on a set of elements, in
ascending order |
|
ThenByDescending |
Performs a secondary sort on a set of elements,
in descending order. |
Set Operators:
Set operators in LINQ refers to the operators that are used
to produce result set based on the presence or absence of the equivalent
elements within the same or separate collection.
Set operators are
|
Operator |
Description |
|
Distinct |
Removes duplicate values from a collection |
|
Except |
Removes elements from a collection that are not
common to another collection |
|
Intersect |
Retrieves common elements from two collections. |
Filter Operators:
Filter operators refer to an operation that modifies a
result set according to the specified condition in such a manner that it
contains only those elements that satisfy a specified condition. The filter
operators are.
|
Operator |
Description |
|
OfType |
Selects those values from a set of values that
can be converted to a specified type |
|
Where |
Selects those values from a set of values that
satisfy a given condition. |
Projection Operators:
Projection operators refer to the operator that transform an
object into new form; The new form generally consists of properties that will
be used subsequently. The new form into which the objects are transformed is of
a new type. The projection operators are
|
Operator |
Description |
|
Select |
Projects(selects) values from a single sequence
or collection |
|
SelectMany |
Projects(selects) values from multiple sequence
or collections |
Q.EXPLAIN SORTING OPERATORS
IN LINQ
Sorting Operators in LINQ are used to change the order or sequence
of the data (either ascending or descending), which is based on one or more
attributes.
Sorting Operators available in LINQ are:
- ORDER
BY
- ORDER
BY DESCENDING
- THEN
BY
- THEN
BY DESCENDING
- REVERSE
|
Operator |
Description |
Query Syntax |
|
OrderBy |
This operator will sort the values in ascending order. |
ordeby |
|
OrderByDescending |
This operator will sort the values in descending order. |
Orderby ......descending |
|
ThenBy |
This operator is used to perform the secondary sorting in
ascending order. |
Orderby...,.... |
|
ThenByDescending |
This operator is used to perform the sorting in descending
order. |
Orderby....,....descending |
|
Reverse |
This operator is used to reverse the order of elements in the
collection. |
Not applicable |
EX:
Double
click on button and add the
following code
double[]
doubles={500,700,100,200,400,600,900,300,800};
listview1.Items.Clear();
var
sorting=from d in doubles
orderby d
select d;
foreach(var
d in sorting)
{
Listview1.Items.Add(d.ToString());
}
Q. Explain
SET operator in LINQ.
LINQ Set Operations
In LINQ, Set Operators are used to return the
set of the result based on the presence or absence of equivalent elements
within the same or separate collections.
In LINQ, we have different types of set
operators available. These are:
- UNION
- INTERSECT
- DISTINCT
- EXCEPT
|
Operators |
Description |
|
UNION |
Union operator combines
multiple collections into single collection and return the resultant collection
with unique element. |
|
INTERSECT |
It returns the element in
a sequence, which is common in both the input sequence. |
|
DISTINCT |
It removes the duplicate
elements from the collection and returns the collection with unique values. |
|
EXCEPT |
It returns the sequence
element from the first input sequence, which is not present in the second
input sequence. |
EX:
DOUBLE CLICK ON BUTTON AND ADD THE
FOLLOWING CODE
IList<string> strList1 = new List<string>() { "One", "Two", "three", "Four" };
IList<string> strList2 = new List<string>() { "Two", "THREE", "Four", "Five" };
var result = strList1.Union(strList2);
foreach(string str in result)
listview1.Items.Add(str.ToString());
Q. EXPLAIN Grouping
operators in LINQ
The grouping operator in LINQ is used to put data into
groups so
that the elements in each group share a common attributes.
The group clause is the grouping operator used in LINQ.
The group clause returns a sequence of the
IGrouping<Tkey,
TElement> objects that contain zero or more items
that match
the key value for the group.
Double click on
button and add the following code
String[] words={“apple”,”banana”,”pineapple”,”apricot”,”papaya”,”blueb
erry”,”abascus”,”cherry”,”parrot”,”black”};
var groupwords=from w in words
group w by w[0] into g
select new {FirstLetter=g.key,words=g};
foreach(var g in groupwords)
{
Listview1.Items.Add(“words that starts from
letter:”+g.FirstLetter.TOstring());
{
Foreach(var w in g.words)
{
Listview1.Items.Add(w);
}
}
Q. EXPLAIN FILTERING OPERATORS LINQ.
EX:
Double click on
button and add the following code
Int[]
numbers={5,10,15,20,25,30,35,40,45,50,55,60,65,70,75,80,85,90,95};
Var mynums=from n in numbers
Where
n>25
Select
n;
foreach(var x in mynums)
{
Listview1.Items.Add(x.ToString());
}
Q. Explain PARTITION OPERATOR IN
LINQ?
LINQ Partition
Operator
In LINQ, Partition Operators are used to
partition the list/collections items into two parts and return one part of the
list items. Here are the different types of partitioning operators available in
LINQ.
- TAKE
- TAKEWHILE
- SKIP
- SKIPWHIL
|
Operator |
Description |
Query-Syntax |
|
TAKE |
This operator is used to
return the specified number of elements in the sequence. |
Take |
|
TAKEWHILE |
This operator is used to return
the elements in the sequence which satisfy the specific condition. |
Takewhile |
|
SKIP |
This operator is used to
skip the specified number of elements in a sequence and return the remaining
elements. |
Skip |
|
SKIPWHILE |
This operator is used to
skip the elements in a sequence based on the condition, which is defined as
true. |
Skipwhile |
EX:
//create an array countries of string type with the initialized array
string[] countries = { "India", "USA", "Russia", "China", "Australia", "Argentina" };
//here take() method will return the value from the String array upto three numbers.
IEnumerable<string> result = countries.Take(3);
foreach (string s in result)
{
Listview1.Items.Add(s.ToString());
}
Q.EXPLAIN PROJECTION OPERATORS
IN LINQ.
Projection Operators: Select, SelectMany
There are two projection
operators available in LINQ.
1)
Select 2) SelectMany
2) Select is used to select value from a collection whereas SelectMany is used to select values from a
collection of collection i.e. nested collection.
3) Select and SelectMany both
are projection operators. In below example we will return a list of courses,
each containing a list of subjects. You will see that Select will return a list
of lists of subjects while SelectMany will flatten the lists into a single list
of subjects.
List<string> animals = new List<string>() { "cat", "dog", "donkey" };
List<int> number = new List<int>() { 10, 20 };
var mix = number.SelectMany(num =>
animals, (n, a) => new { n, a });
the mix will have
following elements in flat structure like
{(10,cat), (10,dog), (10,donkey), (20,cat), (20,dog), (20,donkey)}
Q.Explain Joins in Linq.
There are Different Types of SQL
Joins which are used to query data from more than one database
tables. In this article, you will learn about how to write SQL joins queries in
LINQ using C#. LINQ has a JOIN query operator that gives you SQL JOIN like behavior and
syntax.
Types of LINQ Joins
- INNER JOIN: Inner Join only return matched records between
two or more tables based on a common field between these tables.
- LEFT OUTER JOIN: Return all rows from the left table, and the
matched rows from the right table.
- RIGHT JOIN: Return all rows from the right table, and the
matched rows from the left table.
- FULL JOIN: Return all rows when there is a match in ONE of the tables.
using System;
using System.Linq;
namespace JOINS_LINQ
{
public partial class WebForm1 : System.Web.UI.Page
{
protected void PageLoad(object sender, EventArgs e)
{
LeftOuterJoin();
RightOuterJoin();
Concat();
}
public void LeftOuterJoin()
{
var db = new DataClasses1DataContext();
var query = from p in db.Employees
join r in db.Students
on p.EmpId equals r.PersonId into temp
from t in temp.DefaultIfEmpty()
select new
{
Designation
= p.EmpDesignation,
EmployeeName = p.EmpName,
FirstName = t.FirstName,
LastName = t.LastName,
Age = t.Age
};
GridView1.DataSource = query;
GridView1.DataBind();
}
protected void Concat()
{
var db = new DataClasses1DataContext();
var query1
= from r in db.Students select r.FirstName;
var query2
= from p in db.Employees select p.EmpName;
var concatquery =
query1.Concat(query2);
GridView3.DataSource = concatquery;
GridView3.DataBind();
}
protected void RightOuterJoin()
{
var db = new DataClasses1DataContext();
var query = from r in db.Students
join p in db.Employees
on r.PersonId equals p.EmpId into temp
from t in temp.DefaultIfEmpty()
select new
{
FirstName = r.FirstName,
LastName = r.LastName,
Age = r.Age,
Designation = t.EmpDesignation,
EmployeeName = t.EmpName
};
GridView2.DataSource = query;
GridView2.DataBind();
}
}
}
Q) Explain LINQ TO ADO.NET
Linq to ADO.NET is the term that describes the database
–centric
aspects of Linq.
Linq to Ado.net consists of two separate technologies
1) LINQ to SQL
2) LINQ to DataSet
LINQ to SQL
Following are the basic steps to add LINQ to SQL:
1. Open a new project.
2. Add a new database connection using the Server Explorer.
3. From Server Explorer, right click on Data Connections and
click the Add
Connection option. Following is the snapshot of the Server
Explorer,
4. From Add Connection window, select the Server name where
the SQL server
is installed or enter the complete path of the target SQL
server instance name
in the Server Name text box.
5. Now select the target database name from the Select menu
or enter a
database name dropdown list and click Ok. Following is the
snapshot of the
Add Connection window,
6. Now to add LINQ to SQL, right click on the project name
from the Solution Explorer
and click the Add option then click the New Item option.
Following is the snapshot of
the Add New Item window,
7. Now from Add New Item window, click on LINQ to SQL
classes. The default name of
the LINQ to SQL classes is DataClasses1.dbml. We can also
change the default
name to any other name. Following is the snapshot,
8. Now select the required tables from the server Explorer
and drag into the
DataClasses1.dbml left side panel
9. The LINQ to SQL classes (DataClasses1.dbml) has a toolbox
which we can use to
set the associations or relationships between the tables.
10. When the LINQ to SQL Classes is created and the required
tables are added
then it creates a DataContext DataClasses1DataContext. The
DataClasses1DataContext is the default name of the
DataContext and it depends on
the name of the DataClasses1.dbml. Following is the snapshot
of the
DataClasses1DataContext.dbml,
11. Now LINQ to SQL is ready to use. Just declare an object
from the created
DataContext DataClasses1DataContext and performs LINQ query
on this object.
UNIT –V
Q. Explain ASP.NET FEATURES.
ASP.NET Web Forms
Features
ASP.NET is full of features and provides an
awesome platform to create and develop web application. Here, we are discussing
these features of Web Forms.
- Server
Controls
- Master
Pages
- Working
with data
- Security
- Performance
- Error
Handling
Server
Controls
Web Forms provides rich set of server controls. These controls are
objects that run when the page is requested and render markup to the browser.
- Performance
- Error
Handling
Master
Pages
It allowsus to create a consistent layout for the pages in our
application. This page defines the look and feel and standard behavior that we
want for all of the pages in our application.
Working
with Data
In an ASP.NET Web Forms application, we use data-bound controls to
automate the presentation or input of data in web page UI elements such as
tables and text boxes and drop-down lists.
Security
Developing a secure application is most important aspect of
software development process. ASP.NET Web Forms allow us to add extensibility
points and configuration options that enable us to customize various security
behaviors in the application.
Performance
Web Forms provides good performance and allows us to modify
performance related to page and server control processing, state management,
data access, application configuration and loading, and efficient coding
practices.
Debugging
and Error Handling
We can diagnose problems that occur in our Web Forms application.
Debugging and error handling are well supported within ASP.NET Web Forms so
that our applications compile and run effectively.
Explain
validation controls
Validation
Controls in ASP.NET
Validation is a process of testing and
ensuring that the user has entered required and properly formatted information
through the web form.
There are six types of
validation controls in ASP.NET
1.
RequiredFieldValidation Control
2.
CompareValidator Control
3.
RangeValidator Control
4.
RegularExpressionValidator Control
5.
CustomValidator Control
6.
ValidationSummary
|
Validation
Control |
Description |
|
RequiredFieldValidation |
Makes
an input control a required field |
|
CompareValidator |
Compares
the value of one input control to the value of another input control or to a
fixed value |
|
RangeValidator |
Checks
that the user enters a value that falls between two values |
|
RegularExpressionValidator |
Ensures
that the value of an input control matches a specified pattern |
|
CustomValidator |
Allows
you to write a method to handle the validation of the value entered |
|
ValidationSummary |
Displays
a report of all validation errors occurred in a Web page |
RequiredFieldValidator
RequiredFieldValidator control
is used to checks data is entered into the attached control.
The syntax of the required
Field control
<asp:RequiredFieldValidator
ID="rfvcandidate"
runat="server" ControlToValidate
="ddlcandidate"
ErrorMessage="Please choose a
candidate"
InitialValue="Please choose a
candidate">
</asp:RequiredFieldValidator>
CompareValidator
Compare validator is used to
compare the value of two controls or with a fixed value. It has the following
specific properties:
|
Properties |
Description |
|
Type |
It specifies the data type. |
|
ControlToCompare |
It specifies the value of the input
control to compare with. |
|
ValueToCompare |
It specifies the constant value to compare
with. |
|
Operator |
It specifies the comparison operator, the
available values are Equal, NotEqual, GreaterThan, GreaterThanEqual,
LessThan, LessThanEqual, and DataTypeCheck. |
RangeValidator Control
Range validator is used to
validate the input value falls within a predetermined range.
<asp:RangeValidator
ID="rvclass" runat="server"
ControlToValidate="txtclass"
ErrorMessage="Enter
your class (6 - 12)" MaximumValue="12"
MinimumValue="6"
Type="Integer">
</asp:RangeValidator>
RegularExpressionValidator
The RegularExpressionValidator
is used to validating the input value by matching against a pattern of a
regular expression and it is set in the ValidationExpression property.
The syntax of the Regular
Expression control is as given:
<asp:RegularExpressionValidator ID="string" runat="server" ErrorMessage="string"
ValidationExpression="string" ValidationGroup="string">
</asp:RegularExpressionValidator>
CustomValidator
The custom validator is
used both the client side and the server side validation. It allows
writing application-specific custom validation routines.
The basic syntax for the control
is as given:
<asp:CustomValidator ID="CustomValidator1" runat="server"
ClientValidationFunction=.cvf_func. ErrorMessage="CustomValidator">
</asp:CustomValidator>
ValidationSummary
Validation summary does not
perform any validation but shows a summary of all errors on the page. It
has the following specific properties:
|
Properties |
Description |
|
ShowSummary |
shows the error messages in a specified
format. |
|
ShowMessageBox |
shows the error messages in a separate
window. |
The syntax for the validation
summary control is as given:
<asp:ValidationSummary ID="ValidationSummary1" runat="server"
DisplayMode = "BulletList" ShowSummary = "true" HeaderText="Errors:" />
Explain The
Request & Response object
When a
browser asks for a page from a server, it is called a request. The ASP Request
object is used to get information from the user. Its collections, properties,
and methods are described below:
Collections CollectionDescription
ClientCertificate Contains all the field values stored in the client certificate
Cookies Contains
all the cookie values sent in a HTTP request
Form Contains
all the form (input) values from a form that uses
the post method
QueryString Contains
all the variable values in a HTTP query string
ServerVariables Contains all the
server variable values
•
Response Object
The ASP Response object is used to send output
to the user from the server. Its collections, properties, and methods are
described below
•
Method Description
•
AddHeader Adds
a new HTTP header and a value to the
HTTP response
•
Clear Clears
any buffered HTML output
•
End Stops
processing a script, and returns the current result
•
Flush Sends
buffered HTML output immediately
•
Redirect Redirects
the user to a different URL
•
Write Writes
a specified string to the output
EXPLAIN CREATING WEB FORM IN ASP.NET
1-
Start -> All Programs -> Visual Studio
2008
2-
Now go to File Menu -> New -> Web Site
3-
3- Under Visual Studio Installed Template->
Choose ASP.NET WEB SITE -> ChooseFile System from the location combo box
-> Set the path by the browse button - > Choose the language from the
Language Combo Box (Visual C# , Visual Basic , J #)
4-
choose Visual C#
5-
Click on the OK Button
6-
Click on this tab and you will see a blank web
page where you can drag any control from the toolbox (which is in the left side
of this window)
7-
If you are not able to see the Toolbox
window just go to View -> Choose Toolbox .
8-
Drag a button on the blank page and now click
on the Source tab (in the bottom of this page)
9-
Now you can drag any control from the toolbox
to the blank web page and you can set the properties of these controls from the
property window
10-
If You are not able to see the property window
just go to View - > Select Properties Window
11-
A new window will open on the right side of
this page…
12-
Select the control for which you want to set
the properties
13-
go to properties window and set the properties
like Button Name
14- If you want to change the Button name which
you have added in your web site then select
15- the button and right click on the button
select properties and the select the — Text Property from the property window
and give any name which you want
EXPLAIN COMPARING SERVER AND CLIENT VALIDATION
IN ASP.NET.
·
validation
Validation is a process of testing and
ensuring that the user has entered required and properly formatted information
through the web form.
·
Client-side
validation
In client-side validation method, all the
input validations and error recovery process is carried out on the client side
i.e on the user’s browser. It can be done using JavaScript, AJAX, HTML5 etc.
·
Server-side
validation
In server-side validation, all the input
validations and error recovery process is carried out on the server side. It
can be done using programming languages like C#.NET, VB.NET etc.
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