FileLoadException with Telerik.Licensing.Runtime After Upgrading to 2026.3.812
Environment
| Product | UI for ASP.NET AJAX |
| Version | 2026.3.812 |
Description
I encounter the following error after upgrading to UI for ASP.NET AJAX 2026.3.812 and Licensing 1.9.1:
Could not load file or assembly 'Telerik.Licensing.Runtime, Version=1.8.2.0, Culture=neutral, PublicKeyToken=98bb5b04e55c09ef' or one of its dependencies.
This issue occurs even though no binding redirects are present in the web.config file.
Cause
The error arises from leftover references to older Telerik assemblies, such as Telerik.Web.Spreadsheet.dll or other outdated Document Processing Library assemblies, still present in the bin folder or project references. These old assemblies reference Telerik.Licensing.Runtime, Version=1.8.2.0, which conflicts with the updated Licensing 1.9.1 runtime.
Starting with version 2026 Q3 (2026.3.812), the RadSpreadsheet component uses a new dependency, Telerik.Spreadsheet.Web, which is distributed as a standalone NuGet package. The old Telerik.Web.Spreadsheet.dll is no longer valid in this version. Therefore, the rename from Telerik.Web.Spreadsheet.dll to Telerik.Spreadsheet.Web.dll occurred in Telerik UI for ASP.NET AJAX 2026.3.812.
Solution
-
Check the
binfolder and deployment packages for leftover assemblies, such asTelerik.Web.Spreadsheet.dll, and delete them. -
Update all project references to the following:
Telerik.LicensingTelerik.Web.UI- Replace
Telerik.Web.Spreadsheetwith the new dependency,Telerik.Spreadsheet.Web. Add it via NuGet or from theAdditionalLibraries/Bin462folder in the Telerik installation package if theRadSpreadsheetcomponent is used.
-
Review Document Processing Library references for stale or duplicate files, but do not remove an assembly solely because its file name begins with
Telerik.Windows. The platform-agnostic namespace migration changes source namespaces, while supported assembly identities can retainTelerik.Windows.Documents.*andTelerik.Windows.Zipnames. Compare the resolved package assets, assembly versions, and deployed files for the target framework before removing anything. For RadGrid XLSX export, follow the Excel XLSX export requirements; theTelerik.Spreadsheet.Webdependency is specific to RadSpreadsheet. -
Review the Release History for Telerik UI for ASP.NET AJAX 2026 Q3 (2026.3.812) for additional breaking changes or updates.
If the error still requests an older runtime version, such as 1.6.16.0, do not assume that the NuGet package version or file version is the CLR assembly version. Check the following values separately:
- Inspect
obj/project.assets.jsonand the transitive package graph for every project that contributes assemblies to the application. - Inspect the deployed
Telerik.Licensing.Runtime.dllwith an assembly inspection tool and record itsAssemblyVersion, file version, public key token, and physical path. - Identify the assembly that contains the reference to the requested runtime version by using .NET Framework Fusion logging or equivalent loader diagnostics.
- Check all
binand publish directories, the GAC, andweb.configbinding redirects for duplicate or stale copies. If you add a redirect, setnewVersionto the verifiedAssemblyVersionof the deployed DLL; do not copy a package version intonewVersionwithout verifying the assembly metadata. - Delete stale
bin,obj, publish output, and ASP.NET temporary files, then restore, rebuild, and redeploy the application. Confirm that the final deployment contains one intended runtime assembly.
The reported version must therefore be identified as a package version, file version, or CLR AssemblyVersion before a binding redirect can be evaluated. The example version in the exception identifies the assembly requested by a compiled dependency; it does not by itself identify the version that should be deployed.