check this coding once which for displaying captcha image

[readnlearn]

hai,
i have written this below code for displaying captcha image whenever i entered incorrect uname,password in login page.
for that i disable the controls of captcha like textbox,labels, button and image control in source code of designing part.
and i enable those controls in an if condition which display captcha.
but if i entered correct information which is in database
it shouldn't navigate to the corresponding page
and also if entered incorrect data it shouldn't displys captcha.
whats problem behind this coding?
check it
and give correct code for this one if any.


namespace CaptchaImage
{
public partial class DefaultImage : System.Web.UI.P age
{
static int a = 0;
protected void Page_Load(objec t sender, EventArgs e)
{
if (!this.IsPostBa ck)

// Create a random code and store it in the Session object.
this.Session["CaptchaImageTe xt"] = GenerateRandomC ode();

else
{
// On a postback, check the user input.
if (this.CodeNumbe rTextBox.Text ==
this.Session["CaptchaImageTe xt"].ToString())
{
// Display an informational message.
this.MessageLab el.CssClass = "info";
this.MessageLab el.Text = "Correct!";
}
else
{
//Display an error message.
this.MessageLab el.CssClass = "error";
this.MessageLab el.Text = "ERROR: Incorrect, try again.";

// Clear the input and create a new random code.
this.CodeNumber TextBox.Text = "";
this.Session["CaptchaImageTe xt"] = GenerateRandomC ode();
}
}

}
private Random random = new Random();
private string GenerateRandomC ode()
{
string s = "";
for (int i = 0; i < 6; i++)
s = String.Concat(s , this.random.Nex t(10).ToString( ));
return s;
}

#region Web Form Designer generated code
override protected void OnInit(EventArg s e)
{

// CODEGEN: This call is required by the ASP.NET Web Form Designer.

InitializeCompo nent();
base.OnInit(e);
}

//<summary>
// Required method for Designer support - do not modify
// the contents of this method with the code editor.
// </summary>
private void InitializeCompo nent()
{
this.Load += new System.EventHan dler(this.Page_ Load);

}
#endregion

protected void Button1_Click(o bject sender, EventArgs e)
{
SqlConnection con = new SqlConnection(" initial catalog=rajitha ;data source=sys01;us er id=sa");

con.Open();
// SqlDataReader dr = null;
SqlCommand cmd = new SqlCommand();
cmd.Connection = con;
cmd.CommandText = "select Emailid,passwor d from tbl_registratio n where Emailid='" + TextBox1.Text + "' and password='" + TextBox2.Text + "'";
cmd.CommandType = CommandType.Tex t;
SqlDataReader dr = cmd.ExecuteRead er();
// string uname = TextBox1.Text;
//string pwd = TextBox2.Text;
// if (dr.HasRows)
// {
if (dr.Read())
{
Session["Emailid"] = TextBox1.Text;
Session["password"] = TextBox2.Text;
// if (uname == dr["Emailid"].ToString() && pwd == dr["password"].ToString())
Server.Transfer ("Default2.aspx ");
return;
}
else
{
Response.Write( "you have entered incorrect user name,password") ;
// label3.Text = "you have entered incorrect username,passwo rd";
a = a + 1;
if (a > 2)
{
lb1.Enabled = true;
lb2.Enabled = true;
lb3.Enabled = true;
CodeNumberTextB ox.Enabled= true;
rfd.Enabled=tru e;
MessageLabel.En abled=true;
SubmitButton.En abled = true;
img1.Visible =true;
}
}
}
con.Close();
}
}

}