Another Session variable question

[mpdillon]

If I test against a Session variable before I assign a value to it I get the following error.
"Object reference not set to an instance of an object"
How do I determine if the Session variable exists before I test it?
(I read elsewhere that you could assign the contents of a Session variable to another varible and this would yield a value of "". I tried this but still got the same error message.)
thanks

Context: I want to store the choice of radio buttons on a page. When the user navigates back to this page I want to use the session variable to set the choice they had made previously. Works fine except for the first time they load the page.

 

[mpdillon]

Solution

To test if a session variable has been set, use:

If Session("VariableName") is nothing then
'VariableName was never created
else
'VariableName was created and it is OK to test it for content
If len(Session("VariableName").ToString)> 0 then
'Do Something
else
'Do Something else
end if
end if

This should have been easy for me but wasn't. Before the original post I couldn't find anything about the error message when I searched online. Today I tried again and found it.