Reporting Services report parameter NULL value

Issue: Unable to pass NULL value to the parameter of a report through URL from .NET code.
Solution: In the url add the parameter isNull = true in order to make it accept null value and display the report.
Here is what i had to do, I had a report with 2 parameters. State, Counties.
When I click on a State on the map I wanted to see the report filtered by the selected State and all its counties.
When I click on a county I wanted to see the report filtered by both state and county.
so after creating the report and modifying the dataset as per this article “”
I appended parameter2:isNULL=True when the parameter2 was not passed.
When it was passed, i gave parameter2=value;
Worked like a charm!
Good luck!