SSRS check for blank parameters

Within an SSRS .rdl file you may want to check to see if a Parameter is null before you try to filter results, below are a couple solutions:

=IIf((LEN(Parameters!range.Value)>0), Parameters!range.Value, Fields!range.Value)

=IIf(IsNothing(Parameters!range.Value), Fields!range.Value, Parameters!range.Value)