Whenever I'm using strings in expressions in an RDLC report the report crashes

Question

Whenever I'm using strings in expressions in an RDLC report the report crashes

Haesen, Bart 0

I'm relying heavily on RDLC reports in my web forms applications. I'm using the latest version through Nuget.

Whenever I'm using a string in the expression builder I receive the following error:

Microsoft.Reporting.WebForms.LocalProcessingException: An error occurred during local report processing. ---> Microsoft.Reporting.DefinitionInvalidException: The definition of the report 'xxxx.rdlc' is invalid. ---> Microsoft.ReportingServices.ReportProcessing.ReportProcessingException: An unexpected error occurred while compiling expressions. Native compiler return value: ‘[BC31424] Type 'System.CodeDom.Compiler.GeneratedCodeAttribute' in assembly 'System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' has been forwarded to assembly 'System.Private.CoreLib'. Either a reference to 'System.Private.CoreLib' is missing from your project or the type 'System.CodeDom.Compiler.GeneratedCodeAttribute' is missing from assembly 'System.Private.CoreLib'.’. at Microsoft.ReportingServices.RdlExpressions.ExprHostCompiler.ParseErrors(CompilerResults results) at Microsoft.ReportingServices.RdlExpressions.ExprHostCompiler.InternalCompile(AppDomain compilationTempAppDomain, Boolean refusePermissions) at Microsoft.ReportingServices.RdlExpressions.ExprHostCompiler.<>c__DisplayClass33_0.<Compile>b__0() at Microsoft.ReportingServices.Diagnostics.RevertImpersonationContext.<>c__DisplayClass1_0.<Run>b__0(Object state) at System.Security.SecurityContext.Run(SecurityContext securityContext, ContextCallback callback, Object state) at Microsoft.ReportingServices.Diagnostics.RevertImpersonationContext.Run(ContextBody callback) at Microsoft.ReportingServices.RdlExpressions.ExprHostCompiler.Compile(IExpressionHostAssemblyHolder expressionHostAssemblyHolder, AppDomain compilationTempAppDomain, Boolean refusePermissions, PublishingVersioning versioning) at Microsoft.ReportingServices.ReportPublishing.ReportPublishing.Phase3(ParameterInfoCollection& parameters, Dictionary`2& groupingExprCountAtScope) at Microsoft.ReportingServices.ReportPublishing.ReportPublishing.InternalCreateIntermediateFormat(Stream definitionStream, String& description, String& language, ParameterInfoCollection& parameters, DataSourceInfoCollection& dataSources, DataSetInfoCollection& sharedDataSetReferences, UserLocationFlags& userReferenceLocation, ArrayList& dataSetsName, Boolean& hasExternalImages, Boolean& hasHyperlinks, Byte[]& dataSetsHash) at Microsoft.ReportingServices.ReportProcessing.ReportProcessing.CompileOdpReport(PublishingContext reportPublishingContext, PublishingErrorContext errorContext, String& reportDescription, String& reportLanguage, ParameterInfoCollection& parameters, DataSourceInfoCollection& dataSources, DataSetInfoCollection& sharedDataSetReferences, UserLocationFlags& userReferenceLocation, ArrayList& dataSetsName, Boolean& hasExternalImages, Boolean& hasHyperlinks, Byte[]& dataSetsHash) at Microsoft.ReportingServices.ReportProcessing.ReportProcessing.CreateIntermediateFormat(PublishingContext reportPublishingContext) at Microsoft.Reporting.ReportCompiler.CompileReport(ICatalogItemContext context, Byte[] reportDefinition, Boolean generateExpressionHostWithRefusedPermissions, ControlSnapshot& snapshot) --- End of inner exception stack trace --- at Microsoft.Reporting.ReportCompiler.CompileReport(ICatalogItemContext context, Byte[] reportDefinition, Boolean generateExpressionHostWithRefusedPermissions, ControlSnapshot& snapshot) at Microsoft.Reporting.LocalService.GetCompiledReport(PreviewItemContext itemContext, Boolean rebuild, ControlSnapshot& snapshot) at Microsoft.Reporting.LocalService.CompileReport() at Microsoft.Reporting.WebForms.LocalReport.EnsureExecutionSession() --- End of inner exception stack trace --- at Microsoft.Reporting.WebForms.LocalReport.EnsureExecutionSession()

Below are some expressions I tried, they al return the above error message:

="Some text"
="Last update: " & Format(Globals!ExecutionTime,"yyyy-MM-dd")

Lakshmi Narayana Garikapati 1,315 Reputation points Microsoft External Staff Moderator

2025-10-23T10:37:34.1566667+00:00
Thanks for sharing the details. Before I propose a solution, could you please clarify a few points so I can better understand your setup?

Environment & Setup

Which .NET version are you targeting (e.g., .NET Framework 4.x, .NET Core, .NET 6/7)?

Which RDLC NuGet package version are you using?

Are you running the report in WebForms, WinForms, or ASP.NET Core?

Error Context

Does the error occur only with string expressions, or also with numeric/date expressions?

Does it happen at runtime, during design-time preview, or both?

Is this issue consistent across all reports, or only specific ones?

Expression Details

What types of expressions are you using? (Static text, concatenation, conditional logic, custom functions?)

Have you tried using dataset fields instead of inline VB expressions? If yes, what was the outcome?

Project Configuration

Do you have System.CodeDom referenced in your project?

Which RDLC viewer are you using? (e.g., Microsoft.ReportingServices.ReportViewerControl.WebForms)

Troubleshooting Attempts

Have you tried removing expressions and running the report? Did it work then?

Did you attempt adding missing assemblies or updating NuGet packages?

Thanks,

Lakshmi.

2 answers

Your answer

Lakshmi Narayana Garikapati 1,315 Reputation points Microsoft External Staff Moderator

2025-10-23T10:37:34.1566667+00:00

Thanks for sharing the details. Before I propose a solution, could you please clarify a few points so I can better understand your setup?

Environment & Setup

Which .NET version are you targeting (e.g., .NET Framework 4.x, .NET Core, .NET 6/7)?

Which RDLC NuGet package version are you using?

Are you running the report in WebForms, WinForms, or ASP.NET Core?

Error Context

Does the error occur only with string expressions, or also with numeric/date expressions?

Does it happen at runtime, during design-time preview, or both?

Is this issue consistent across all reports, or only specific ones?

Expression Details

What types of expressions are you using? (Static text, concatenation, conditional logic, custom functions?)

Have you tried using dataset fields instead of inline VB expressions? If yes, what was the outcome?

Project Configuration

Do you have System.CodeDom referenced in your project?

Which RDLC viewer are you using? (e.g., Microsoft.ReportingServices.ReportViewerControl.WebForms)

Troubleshooting Attempts

Have you tried removing expressions and running the report? Did it work then?

Did you attempt adding missing assemblies or updating NuGet packages?

Thanks,

Lakshmi.

Answer 1

Haesen, Bart 0

Will there be an update on the Nuget packages to enable that functionality again?

Lakshmi Narayana Garikapati 1,315 Reputation points Microsoft External Staff Moderator

2026-01-12T04:11:10.16+00:00

Hi Haesen, Bart,

Thank you for your detailed explanation. It looks like you've already followed the recommended steps, but the issue persists.

To help resolve this further, I recommend raising a support ticket so our support team can assist you directly. Please refer to the following link for instructions on how to create a support ticket:

https://support.serviceshub.microsoft.com/supportforbusiness/create

We appreciate your engagement and thank you for being an active part of the community.

Thanks,

Lakshmi.

Answer 2

Haesen, Bart 0

Environment & Setup

.NET Framework 4.8
Microsoft RDLC Report Designer 18.0.0
WebForms

Error Context

I tried following scenarios where the error occurs:

Textbox with only pagenumber: =Globals!PageNumber
Textbox with current date time: =Now() and =FormatDateTime(Now(),DateFormat.ShortDate)
Textbox with user ID: =User!UserID

The error happens at runtime, there is no design time preview.
It's consistent through all reports

Expression Details

The expressions are string concatenations: static text with values from the data source.

Using only values from the data source e.g.: =First(Fields!DateFrom.Value, "NeedCompletionData") works fine.

A Tablix with data from the data source works fine.

When you use static text with data source fields it crashes: ="Date From: " & First(Fields!DateFrom.Value, "NeedCompletionData")

Project Configuration

System.CodeDom is not referenced in the project as I expect everything to get reference by adding the NuGet packages.

I'm using Microsoft.ReportingServices.ReportViewerControl.WebForms 150.1652.0

Troubleshooting attempts

Yes I have tried removing the expressions. As stated above then it works, but this is no option.

I added System.CodeDom through NuGet package 9.0.10, but that did not change the behavior.

Lakshmi Narayana Garikapati 1,315 Reputation points Microsoft External Staff Moderator

2025-10-29T06:25:31.03+00:00

Hi @ Haesen, Bart,

Thanks for sharing the detailed error trace and setup. This issue stems from RDLC’s VB.NET expression compiler failing at runtime due to missing support for System.CodeDom.Compiler.GeneratedCodeAttribute in .NET environments using ReportViewer via NuGet. Expressions like string concatenation or formatting (e.g., ="Date From: " & First(...)) trigger this crash. As a workaround, move such logic to your code-behind by passing preformatted strings as report parameters, or downgrade to .NET Framework 4.8 where VB expression compilation is fully supported.

Thanks,

Lakshmi.
Lakshmi Narayana Garikapati 1,315 Reputation points Microsoft External Staff Moderator

2025-11-03T17:10:18.45+00:00

@Haesen, Bart ,

I’m following up to check if the response provided below was helpful.

Please let us know if your issue has been resolved. If you still have any questions or need further assistance, don’t hesitate to get in touch we’re happy to continue supporting you.

We appreciate your participation and thank you for being an active member of the community.

Best regards,

Lakshmi
Lakshmi Narayana Garikapati 1,315 Reputation points Microsoft External Staff Moderator

2025-11-06T08:59:39.5366667+00:00

Hi @Haesen, Bart,

I’m following up to check if the response provided below was helpful.

Please let us know if your issue has been resolved. If you still have any questions or need further assistance, don’t hesitate to get in touch we’re happy to continue supporting you.

We appreciate your participation and thank you for being an active member of the community.

Best regards,

Lakshmi

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Whenever I'm using strings in expressions in an RDLC report the report crashes

2 answers

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