May I know how to pass data from the winform to the reportviewer chart?
For Example:

In WinForm

i wan pass the variable (string strMonth = "Month";) to the reportviewer chart

In ReportVierwer Chart

i want using the variable in the Winform
Example : IIF(strMonth = "Month",Month(Fields!OrderDate.Value),IIF(strMonth = "Year",Year(Fields!OrderDate.Value))

i am new in using a reportviewer and reportviewer chart !!!

You could accomplish that by making, any variable you want to share, global. This way any object in your app can access it. This link gives a pretty example of how to do that.