HTTP 404 error with Response.Redirect - c#-4.0

Question

I'm getting the following error:
HTTP Error 404.0 - Not Found The resource you are looking for has been
removed, had its name changed, or is temporarily unavailable
with the following code:
SqlConnection cn = new SqlConnection(#"Data Source=bpnaidu-pc\sqlexpress;Initial Catalog=UserLogIn;Integrated Security=True;Pooling=False");
cn.Open();
SqlCommand cmd = new SqlCommand( "INSERT INTO regd values('" + ddl_signup.Text + "','" + txt_user.Text + "','" + txtEmail1.Text+ "','" + txtPassword.Text + "','" + txtConPassword.Text + "')", cn);
cmd.ExecuteNonQuery();
Response.Redirect("welcome to "+txt_user.Text.ToString());
Response.Redirect("Home.aspx");
cn.Close();
Where is the problem?

Answer 1

Although the question isn't directly clear, the answer is. The problem is on this line:
Response.Redirect("welcome to "+txt_user.Text.ToString());
Response.Redirect sends a browser to the webpage specified in the parameter, so you're trying to send the browser to a page called "welcome to {...}". I find this unlikely. I suspect what you really want is:
Response.Write("welcome to "+txt_user.Text.ToString());
Response.Write just sends a text string straight into the HTTP output buffer.
However you follow this up immediately with a redirect to Home.aspx, so in reality the line actually does nothing as no sooner have you written the output out that you tell the browser to redirect to a different page, so the user will not see your welcome message.
I'd also like to point out that you're open to a SQL Injection attack as well - your line:
SqlCommand cmd = new SqlCommand( "INSERT INTO regd values('" + ddl_signup.Text + "','" + txt_user.Text + "','" + txtEmail1.Text+ "','" + txtPassword.Text + "','" + txtConPassword.Text + "')", cn);
...is open to a user doing bad things; if txt_user.Text contains the text '); drop table regd; there's a good chance you'll end up with a missing regd table. To fix, you need to use parameterised SQL statements. Rather than correct this here, I strongly recommend you follow up by reading Jeff Atwood's blog article about this and how to mitigate.