Question

I have discovered that in SQL Reporting there might be a problem. I have a ReportViewer on my page and I am sending in parameters using the following method:

List<ReportParameter> myParams = new List<ReportParameter>();  myParams.Add(new ReportParameter('Start_Date', StartDate)); myParams.Add(new ReportParameter('End_Date', EndDate));  ReportViewer1.ServerReport.SetParameters(myParams); 

This works great! But, when I try to set a parameter to null, after running that query, it maintains the previous value rather than setting it to null.

I run this code on another event that executes after the above code:

List<ReportParameter> myParams = new List<ReportParameter>();  myParams.Add(new ReportParameter('Start_Date'));  // I even tried omiting this line.   //(This is the null parameter I wish to pass) myParams.Add(new ReportParameter('End_Date', EndDate));  ReportViewer1.ServerReport.SetParameters(myParams); 

Has anyone come across a work around or a different technique to get this working?

Also if I initially do not define the parameter, then assign the parameter, then do not define the paramter, it maintains the value that was assigned. (These are all postbacks, each event)

Answer 1

Do something like this..I’ve tested it in my own little test project and it seems to work.

List<ReportParameter> myParams = new List<ReportParameter>();  ReportParameter p = new ReportParameter('Start_Date'); p.Values.Add(null); myParams.Add(p);  //myParams.Add(new ReportParameter('Start_Date'));  // I even tried omiting this line.   //(This is the null parameter I wish to pass) myParams.Add(new ReportParameter('End_Date', EndDate));  ReportViewer1.ServerReport.SetParameters(myParams);