link a dataset to a rdlc file

I created a report with a rdlc. when I add a dataset to this 开发者_如何学Gofile and I want to use this dataset in expression window, and when I select "fields" item in the "Category" box, Display a message in the third box that says: "Report item not linked to a dataset." What I can do to link this dataset to my report.

It is probably easier to user the 'Report Wizard' option which will setup everything correctly. Then you have a choice of layout your report as you want because the wizard will force you to choose a layout, which you may not like :( Of course I am assuming you are using Visual Studio.