C# - Using Statement Example | Uses of Using Statement in C#

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Introduction:

In this article I will explain uses of using statement in c# and how to declare and use using statement in c#, vb.net, Asp.net.

Description:

In Previous posts I explained lot of articles regarding Asp.net, Gridview, SQL Server, Ajax, JavaScript etc. Now I will explain about using statement in c#.

Generally in our applications we will write code like create connection object to handle connectionstring after that open a connection and create command object etc. to interact with database to get data that would be like this

SqlConnection con = new SqlConnection(connectionString);
con.Open();
SqlCommand cmd = new SqlCommand (commandString, con);
cmd.ExecuteNonQuery();
con.Close();
It’s very easy way to write above code but problem is SqlConnection and SqlCommand objects will create IDISPOSABLE interface that means it could create unmanaged resources in our application to cleanup those objects we need to call Dispose() method at the end of our process otherwise those objects will remain in our application.

Suppose we use using statement in our applications it will automatically create try / finally blocks for the objects and automatically runs Dispose() method for us no need to create any try/finally block and no need to run any Dispose() method.

If we use using statement we need to write code will be like this

C# Code

using (SqlConnection con = new SqlConnection(connectionString))
{
using (SqlCommand cmd = new SqlCommand (commandString, con))
{
con.Open();
cmd.ExecuteNonQuery();
}
}
VB.NET Code

Using con As New SqlConnection(connectionString)
Using cmd As New SqlCommand(commandString, con)
con.Open()
cmd.ExecuteNonQuery()
End Using
End Using
In above code using statement no need to worry about close connection because using statement automatically close the connection once process is complete and automatically it will run Dispose() method to dispose objects.

The above using statement code will equal to below code

SqlConnection con = null;
SqlCommand cmd = null;
try
{
con = new SqlConnection(connectionString);
cmd = new SqlCommand(commandString, con);
con.Open();
cmd.EndExecuteNonQuery();
}
finally
{
if (con != null)
con.Dispose();
if (cmd != null)
cmd.Dispose();
}
Sample Code to display data in gridview by using statement

First open Default.aspx page and write the following code
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:GridView ID="gvDetails" runat="server">
</asp:GridView>
</div>
</form>
</body>
</html>
After that open code behind page and add the following namespace references
using System;
using System.Configuration;
using System.Web.Configuration;
After add namespaces write the following code in code behind
C# code
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
BindGridviewData();
}
}
//Bind Data to Repeater Control
protected void BindGridviewData()
{
string connectionString = "Data Source=SureshDasari;Initial Catalog=MySampleDB;Integrated Security=true";
using (SqlConnection con = new SqlConnection(connectionString))
{
using (SqlCommand cmd=new SqlCommand("select * from Repeater_Table Order By PostedDate desc",con))
{
con.Open();
DataTable dt = new DataTable();
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(dt);
gvDetails.DataSource = dt;
gvDetails.DataBind();
}
}
}
VB.NET Code
Imports System.Data
Imports System.Data.SqlClient
Partial Class Default
Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
If Not IsPostBack Then
BindGridviewData()
End If
End Sub
'Bind Data to Repeater Control
Protected Sub BindGridviewData()
Dim connectionString As String = "Data Source=SureshDasari;Initial Catalog=MySampleDB;Integrated Security=true"
Using con As New SqlConnection(connectionString)
Using cmd As New SqlCommand("select * from Repeater_Table Order By PostedDate desc", con)
con.Open()
Dim dt As New DataTable()
Dim da As New SqlDataAdapter(cmd)
da.Fill(dt)
gvDetails.DataSource = dt
gvDetails.DataBind()
End Using
End Using
End Sub
End Class

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