I have created a form-based program that needs some input validation. I need to make sure the user can only enter numeric values within the distance Textbox.

So far, I've checked that the Textbox has something in it, but if it has a value then it should proceed to validate that the entered value is numeric:

```
else if (txtEvDistance.Text.Length == 0)
        {
            MessageBox.Show("Please enter the distance");
        }
else if (cboAddEvent.Text //is numeric)
        {
            MessageBox.Show("Please enter a valid numeric distance");
        }

```