reportbuilder

before going to problem let me clear that i know there are similar questions ask before but could not find the answer of my problem. my problem is: I want to select the Data Source at runtime. First of all, i simply create a report by making a shared data source. then i create a data set using this data source. I run the report and it is working perfectly. Then I create two parameters, one for data source and one for data set. both parameters are type of "Text", their parameter visibility is "Visible" and their Available and Default values are "None". Then I created a second data source which

I'm trying to produce a conditional sum in SQL Server Report Builder 3.0. My expression looks like this: =Sum(Iif(Fields!ProjectTypeID.Value=2,Fields!kWp.Value,0)) I'd hoped that this expression would produce a sum of the kWp of all projects of type 2. Unfortunately, it is not to be. And I can't seem to work out why. It just returns a 0 result, even though I know that there are non-zero values in the kWp column, and the column does not contain nulls. A colleague did manage to get a positive result by replacing the Fields!kWp.Value with 1 * Fields!kWp.Value But we have no idea why this works,