Using substring to validate last 4 digits of a textbox C# (vb6 Right function)
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I am attempting to validate a date text box to make sure the correct date format was entered.

I converted this vb6 code  -

 - If (IsDate(txtBirthDate)) And (IsNumeric(Right(txtBirthDate, 4))))

In to this C# code -


            int output = 1;
            DateTime output2;
           
            if ((! DateTime.TryParse(txtBirthDate.Text, out output2)) & (!int.TryParse((txtBirthDate.Text.Substring(txtBirthDate.Text.Length - 5)), out output))) 
            {
                MessageBox.Show("error")
            }

What I am attempting to do is make sure that the last 4 digits of the date text box are numeric (the year - i.e 1990 in 05/10/1990) and if it is not a number, then show error. Although I cannot verify everything is numeric due to the "/" in the date format.

The code does not show an error and builds. But when I debug the application I receive an error. The error states ---- Index and length must refer to a location within the string.
Parameter name: length. 

Any ideas on how to accomplish this?

Thank you. 

-Eric