Results of Request.Form if the requested input is blank

Question

Hi,

When I use Request.Form("myInput") and the input field "myInput" is blank, I get a server error.

How do I handle this?

Is there a way to check if "myInput" has not been filled?

Answer 1

Reading from the Request.Form collection doesn't cause an exception neither if the value is an emptry string (which happens if the input field is blank) nor if the field doesn't even exist.

If the input field is blank, you get an empty string when reading from the collection, so to check for that you just check if the value of the Length property of the string is zero.

If the input field doesn't exist, you get a null reference (Nothing in VB) when reading from the collection, so to check for that you compare the reference to null (use is Nothing in VB).

To check for both conditions you can use the String.IsNullOrEmpty method.

Answer 2

If Request.Form("myInput") IsNot Nothing Then
    Response.Write(Request.Form("myInput").ToString())
End If

Wrap your code in an If statement to see if you are returning a null from the form. If you try to cast a null ToString() it will throw an exception.

Answer 3

You may try something like

If IsEmpty(Request.Form("myInput")) Then
    // input is empty, display error
Else
    // input has been filled, continue
End If