DevGateway Fails with XML Deserialization Error: Cannot deserialize XML:

[rajan98]

While attempting to register a custom workload using the Microsoft Fabric Workload Development Kit, DevGateway consistently fails with the following error: "Cannot deserialize XML: There is an error in XML document (2, 2)", targeting WorkloadDefinition. The error appears during the registration step after authentication succeeds, and the DevGateway logs indicate a BadRequest response with InvalidParameter. Despite verifying that the WorkloadManifest.xml file is present in the packaged .nupkg file and correctly formatted as UTF-8 without BOM, the issue persists. The environment uses the default sample boilerplate setup with only minor modifications for workload name and structure. This appears to be a blocking issue during the DevGateway registration process.

[v-ssriganesh]

Hi @rajan98,
I wanted to check if you had the opportunity to review the information provided. Please feel free to contact us if you have any further questions. If my response has addressed your query, please accept it as a solution and give a 'Kudos' so other members can easily find it.
Thank you.

[v-ssriganesh]

Hi @rajan98,

May I ask if you have resolved this issue? If so, please mark the helpful reply and accept it as the solution. This will be helpful for other community members who have similar problems to solve it faster.

Thank you.

[Teddyb]

Hi @rajan98 - happy to see you are taking the WDK for a spin 🙂 

Your message suggests that you only made minor modification and haven't yet registered an Entra app and some additional must-do updates to the sample manifest package: Quick start - Run a sample workload - Microsoft Fabric | Microsoft Learn
After making the changes don't forget to run the DevGateway with reference to the re-packaged (step 11) manifest package (.nupkg): https://learn.microsoft.com/en-us/fabric/workload-development-kit/quickstart-sample#step-12-run-the-.... 
Please update us if this helped or any additional errors you encountered.

[v-ssriganesh]

Hello @rajan98,
Thank you for reaching out to the Microsoft fabric community forum. The error that your see it might be cause of XML Structure or Namespace Issue, Configuration Mismatch or Unescaped Characters.

Please consider the below troubleshooting Steps:

• Open WorkloadManifest.xml in a text editor like VS Code to make sure it starts exactly with. There shouldn’t be any extra spaces or hidden characters before this line.

• Compare your WorkloadManifest.xml with the sample provided in the Workload Development Kit. Ensure all required elements (e.g: <AppId>, <RedirectUri>) are present and correctly formatted and Use an XML validator to check against the WorkloadDefinition schema.

• Go back to the untouched sample WorkloadManifest.xml from the kit and test the registration process with it. If it works, compare it side-by-side with your modified version to spot any differences causing the issue.
• Check the DevGateway logs for more details on the BadRequest error. Look for hints about what might be wrong, like an invalid AppId or other fields that aren’t lining up.
• If you’ve added custom names or descriptions in WorkloadManifest.xml, make sure they don’t include characters

• Check you’re using the latest version of Microsoft.Fabric.Workload.DevGateway.exe from Microsoft’s Download Center.

If this information is helpful, please “Accept as solution” and give a "kudos" to assist other community members in resolving similar issues more efficiently.
Thank you.