(Microsoft.Reporting.WebForms.ReportViewer) is not compatible with the type of control (Microsoft.Reporting.WebForms.ReportViewer)

I am trying to use ReportViewer 9 in Visual Studio 8 but I get this error when I try to run the page:

The base class includes the field 'ReportViewer1', but its type (Microsoft.Reporting.WebForms.ReportViewer) is not compatible with the type of control (Microsoft.Reporting.WebForms.ReportViewer).

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What did work for me was going to the Solution Explorer -> [Project Name] -> References -> delete the Report viewer reference and readd the correct one (Microsoft.Reporting.WebForms.ReportViewer 8.0/9.0).

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from: http://forums.asp.net/p/1284295/3398317.aspx