Crystal Report weird error (Unknown Query Engine Error)

Visual Studio da bazen Unknown Query Engine Error hatası alırız. Özellikle de framework 4.0 ile çalışıyorsak ama hemen kararsızlığa düşmeyin tabi ki bir çözümü var

CrystalDecisions.CrystalReports.Engine.DataSourceException: Unknown Query Engine Error
Error in File C:\Users\Magdy\AppData\Local\Temp\rpt_Stock_Cost {DC276D4F-79F4-43B9-8168-24E6B7BF490A}.rpt:
Unknown Query Engine Error ---> System.Runtime.InteropServices.COMException: Unknown Query Engine Error
Error in File C:\Users\Magdy\AppData\Local\Temp\rpt_Stock_Cost {DC276D4F-79F4-43B9-8168-24E6B7BF490A}.rpt:
Unknown Query Engine Error
   at CrystalDecisions.ReportAppServer.Controllers.DatabaseControllerClass.ReplaceConnection(Object oldConnection, Object newConnection, Object parameterFields, Object crDBOptionUseDefault)
   at CrystalDecisions.CrystalReports.Engine.Table.SetDataSource(Object val, Type type)
   at CrystalDecisions.CrystalReports.Engine.ReportDocument.SetDataSourceInternal(Object val, Type type)
   --- End of inner exception stack trace ---
   at CrystalDecisions.ReportAppServer.ConvertDotNetToErom.ThrowDotNetException(Exception e)
   at CrystalDecisions.CrystalReports.Engine.ReportDocument.SetDataSourceInternal(Object val, Type type)
   at CrystalDecisions.CrystalReports.Engine.ReportDocument.SetDataSource(DataSet dataSet)
   at Diamonds.UIL.Forms.frm_ReportViewer.Load_Report(String File_FullPath, DataSet DS) in E:\Development\Bitco\Diamond\Project\Diamond 2.0.1\Diamonds\UIL\Reports\Forms\Viewer\frm_ReportViewer.cs:line 256

işte çözüm

Visual Studio içinde bulunan app.config dosyasının içine aşağıdaki kodları yapıştırın ve Rebuild yapın işlem bu kadar :)

<startup useLegacyV2RuntimeActivationPolicy="true">
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
</startup>