Checking numeric input for textbox in C#

In this article show how to check whether TextBox contain numeric or not in C# whenever you input value to TextBox on event keypress and leave. This example, I am trying to check on three TextBox to make sure that they contain only numeric value. 

Figure 1: Sample Form

I’m going to check  on three TextBox : Customer  ID, Quantity, and Price. Go to the form and select on the three Textbox, and then go to Properties -->click on Events --> double click on KeyPress and Leave. See picture below:

Figure 2: Create event on KeyPress and Leave for textboxs

Code :

private void TxtCustomer_KeyPress(object sender, KeyPressEventArgs e)

{

  TextBox txt = (TextBox)sender;

  if (!(e.KeyChar >= 48 && e.KeyChar <= 57) && !(e.KeyChar == 8))

  {

     //Do what you want do if input value is not numeric

     MessageBox.Show("please input numeric only !");

     txt.Focus(); 

  }

}

private void TxtCustomer_Leave(object sender, EventArgs e)

{

   bool digi = false;

   TextBox txt = (TextBox)sender;

   string number = txt.Text.Trim();

   for (int i = 0; i < number.Length; i++)

   {

     if (!char.IsNumber(number[i]))

     {

       digi = true;

     }

   }

   if (digi)

   {

      //Do what you want do if input value is not numeric

      MessageBox.Show("please input numeric only !");

      txt.Focus();

   }

        }

 Done....Now you will the result as picture below when you input value which is not numeric.