Preview normal in standalone designer but doesn't works in browser

[Gavin]

I am trying to design a report contains a start date and end date, which needs the start and end day of current month, I implemented the logic in a C# assembly and used it in standalone designer, it's works well in designer, but when I embed it in a asp.net web application, I got this error :
Object reference not set to an instance of an object.
at Telerik.Reporting.Expressions.FunctionNode.Eval(Object row, Object context)
at Telerik.Reporting.Processing.ReportParametersManager`1.CalculateValue(P parameter, Object definitionValue, IDictionary`2 newValues, Object data)
at Telerik.Reporting.Processing.ReportParametersManager`1.CalculateParameterProperties(P parameter, IReportParameter parameterDef, IDictionary`2 parameterValues)
at Telerik.Reporting.Processing.ReportParametersManager`1.Calculate(P parameter, IDictionary`2 parameterValues)
at Telerik.Reporting.Processing.ReportParametersManager`1.CalculateParameters(IDictionary`2 parameterValues)
at Telerik.Reporting.Processing.ReportParametersManager`1.get_Parameters()
at Telerik.Reporting.Processing.DocumentParametersManager`1.InitializeMergeMap()
at Telerik.Reporting.Processing.DocumentParametersManager`1..ctor(IReportDocument definition)
at Telerik.Reporting.Processing.DocumentParametersManager..ctor(IReportDocument definition)
at Telerik.ReportViewer.WebForms.ParametersPage.CreateParametersManager(IReportDocument reportDocument)
at Telerik.ReportViewer.WebForms.ParametersPage.get_ParamsManager()
at Telerik.ReportViewer.WebForms.ParametersPage.CreateChildControls()
at System.Web.UI.Control.EnsureChildControls()
at Telerik.ReportViewer.WebForms.ParametersPage.OnPreLoad(EventArgs e)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

If I replace the values of 2 parameters to static values like "2013-01-01", it works.
 How can I achieve this goal ?

[Dev111]

Are there no answers to this question?  I am dealing with the same thing.

[KS]

Hi,

check this - http://www.telerik.com/support/kb/reporting/report-designer/details/deploying-trdx-(xml-report-definition)-that-uses-external-assembly and make sure all parameters have values or are visible.

-KS