title: "Allow Null Value" not working in SSRS
body: <p>I have a parameter in my SSRS report which I have marked as "Allow Null Value". But when I dont send that parameter from my C# code. I get the below error.</p>
  
  <p><em>Message=This report requires a default or user-defined value for the report parameter 'UserID'. To run or subscribe to this report, you must provide a parameter value. (rsReportParameterValueNotSet)</em></p>
  
  <p>Here is the parameter configuration. Available Values and Default Values tabs are marked as "None".</p>
  
  <p>In some conditions, I don't want to send that parameter. But it wont allow. What else am I missing?</p>
  
  <p><img src="https://i.stack.imgur.com/niesQ.png" alt="enter image description here"></p>