Help with Numeric Only Textbox

Hi All,
I have some small problem with adding a function that will allow only numbers into the text box.
Can someone help?

Thanks alot.

Here is the code

Code:

 
using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Drawing; 
using System.Text; 
using System.Windows.Forms; 
using Sybase.Data; 
using Sybase.Data.AseClient; 

namespace SID_Checker 
{ 
public partial class Form1 : Form 
{ 
public Form1() 
{ 
InitializeComponent(); 
} 

private void panel1_Paint(object sender, PaintEventArgs e) 
{ 

} 

private void label1_Click(object sender, EventArgs e) 
{ 

} 


private void button1_Click(object sender, EventArgs e) 
{ 

string ID = SID.Text; 

if (ID == "" || ID == "0" || ID == null) 
{ 
label4.Text = "Are you Kidding Me"; 
return; 
} 

// <--> Sybase Connection String and Query <--> 

AseConnection oAseConn = new AseConnection(); 
oAseConn.ConnectionString = "Data Source=10.161.56.162;" + 
"Port=2024;" + 
"User ID=dbs;" + 
"Password=password"; 
oAseConn.Open(); 

AseCommand getsid = oAseConn.CreateCommand(); 
getsid.CommandText = "select SID_num from Sessions where sid = " + ID; 
Object obj = getsid.ExecuteScalar(); 


AseCommand getname = oAseConn.CreateCommand(); 
getname.CommandText = "select code from SID_info where SID_num = " + obj; 
Object targetname = getname.ExecuteScalar(); 

label4.Text = targetname.ToString(); 
getsid.Dispose(); 
oAseConn.Dispose(); 

} 

private void SID_TextChanged(object sender, EventArgs e) 
{ 

} 
} 
} 

P.S
I tried using the following but it either did nothing or gave me an error.
Please help me place it at the right place in my code.
thanks

Code:

private void textBox1_KeyPress(object sender, KeyPressEventArgs e) 
{ 
if (!char.IsDigit(e.KeyChar) && e.KeyChar != (char)Keys.Back) 
e.Handled = true; 
} 

thanks
Jonny