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.
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#.
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();
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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();
}
}
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VB.NET
Code
Using con As New SqlConnection(connectionString)
Using cmd As New SqlCommand(commandString, con)
con.Open()
cmd.ExecuteNonQuery()
End Using
End Using
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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();
}
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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>
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After
that open code behind page and add the following namespace references
using System;
using System.Configuration;
using System.Web.Configuration;
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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();
}
}
}
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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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9 comments :
What if we define this objects in Constructor and then use them in the method
Is this a better approach ?
for example;
public class PreScreen
{
public int AdvertId { get; set; }
public int QueId { get; set; }
public string QueType { get; set; }
public string Question { get; set; }
SqlConnection ConSqlClust, ConKimchi;
SqlCommand cmd;
SqlDataReader dr;
SqlDataAdapter da;
string query;
DataSet ds;
public PreScreen()
{
ConSqlClust = new SqlConnection(ConfigurationManager.ConnectionStrings["SqlClustConnectionString"].ConnectionString);
ConKimchi = new SqlConnection(ConfigurationManager.ConnectionStrings["KimchiConnectionString"].ConnectionString);
ds - new DataSet();
dr = new SqlDataReader
}
public DataSet GetPreScreen(int AdId, string Scope)
{
cmd = new SqlCommand("SP_Advert_GetPreScreenQuestions", ConKimchi);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("@Scope", Scope);
cmd.Parameters.AddWithValue("@AdvertId", AdId);
da = new SqlDataAdapter(cmd);
try
{
ConKimchi.Open();
da.Fill(ds);
}
catch (Exception ex)
{
Email.SendErrorMessage(ex);
}
finally
{
ConKimchi.Close();
}
if (ds.Tables[0].Rows.Count == 0)
{
ds.Tables[0].Rows.Add(ds.Tables[0].NewRow());
}
return ds;
}
}
USING statement creates try/finally blocks automatically .can you please tell how to handle errors with USING statement in c# how it handles exceptions .
Hi suresh,
thanks for article but am getting an error in user code
invalid object name
how to show data in data gridview from database in c#.
Hi Suresh,
Great Article .... Keep rocking....
Please also explain about dictionary object to read plus write in Excel sheet .....
Regards,
Please also explain about dictionary object to read plus write in Excel sheet .....
Regards,
Your explanation is excellent.
Your explanation is excellent.
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