An Item with the same key has already been added

[Laura]

We are using Telerik Report Viewer in our Web Application. During development and testing on my local machine I all of a sudden began receiving this bug while testing. Any thoughts?

An item with the same key has already been added.

at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
at Telerik.Reporting.Processing.Expressions.ReportExpressionContext.ResolveNameSpaces()
at Telerik.Reporting.Processing.Expressions.ReportExpressionContext..ctor(Type methodInfoSourceType)
at Telerik.Reporting.Processing.ParametersManager`1..ctor(IReportDocument definition, ICollection`1 parameters)
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)

[Steve]

Hi Wenlei,

Our first guess would be that the same object (report parameter) is added twice. Check the report parameter collection for duplicates. 
However, we cannot tell for sure, from the stack trace alone, so if you cannot find the culprit, please open a support ticket and attach a runnable project that exhibits the problem.

Regards,
Steve
the Telerik team