Crystal Reports Set DataSOurce to List Of Object

Message

     Hi
I Have problem Like Below

I have set database Filds of my report by .NetObject(a class in my Project)

When I set DataSource Of report to List of object Like this:

List<Object> objList= new List<Object>();

objList=getListByLinq();
rep.SetDataSource(list);

I recieve this Error:
DataSet does not support System.Nullable<>.

Is there any one to help me???