How to Troubleshoot Microsoft.Azure.WebJobs.Extensions.Http Assembly Loading Error

Microsoft.Azure.WebJobs.Extensions.Http is a NuGet package that provides HTTP triggers and bindings for Azure Functions. It allows you to create serverless HTTP endpoints that can be invoked by HTTP requests. However, sometimes you may encounter an error when using this package, such as:

Could not load file or assembly ‘Microsoft.Azure.WebJobs.Extensions.Http, Version=3.0.12.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35’. The system cannot find the file specified.

This error means that the Azure Functions runtime could not find or load the Microsoft.Azure.WebJobs.Extensions.Http assembly that is required by your function app. This can happen for various reasons, such as incompatible versions, missing dependencies, corrupted files, etc. In this blog post, I will show you some common causes and solutions for this error.

Check Your Package Versions

One of the possible reasons for getting this error is that your package versions are not compatible with each other or with the Azure Functions runtime version. For example, if you are using Azure Functions v4, you need to use Microsoft.Azure.WebJobs.Extensions.Http version 4.x or higher. If you are using Azure Functions v3, you need to use Microsoft.Azure.WebJobs.Extensions.Http version 3.x or lower.

To fix this, make sure that your package versions are consistent and compatible with your Azure Functions runtime version. You can check your package versions by looking at your .csproj file or by using the dotnet list package command. You can also use the dotnet add package command to add or update your packages.

For example, if you are using Azure Functions v4 and you want to use Microsoft.Azure.WebJobs.Extensions.Http version 4.1.3, you can use the following command:

Check Your Dependencies

Another possible reason for getting this error is that your dependencies are missing or invalid. Dependencies are other packages or assemblies that are required by your function app or by the Microsoft.Azure.WebJobs.Extensions.Http package. For example, Microsoft.Azure.WebJobs.Extensions.Http depends on System.Net.Http.Formatting and Newtonsoft.Json packages.

To fix this, make sure that your dependencies are present and valid in your function app folder or bin folder. You can check your dependencies by using the dotnet list package –include-transitive command or by using a tool like Dependency Walker or ILSpy. You can also use the dotnet restore command to restore your dependencies from NuGet.

For example, if you want to restore your dependencies for your function app project, you can use the following command:

Check Your Files

Another possible reason for getting this error is that your files are corrupted or inaccessible. Files are the physical files that contain the code and metadata of your function app or of the Microsoft.Azure.WebJobs.Extensions.Http package. For example, Microsoft.Azure.WebJobs.Extensions.Http.dll is the file that contains the assembly of the package.

To fix this, make sure that your files are intact and accessible in your function app folder or bin folder. You can check your files by using a tool like File Explorer or PowerShell. You can also use the dotnet clean command to delete any intermediate or output files that may be corrupted.

For example, if you want to clean your function app project, you can use the following command:

Conclusion

In this blog post, I showed you how to troubleshoot Microsoft.Azure.WebJobs.Extensions.Http assembly loading error. This error occurs when the Azure Functions runtime could not find or load the Microsoft.Azure.WebJobs.Extensions.Http assembly that is required by your function app. This can happen for various reasons, such as incompatible versions, missing dependencies, corrupted files, etc. To fix it, you need to check and correct these factors and try again.

I hope you found this post helpful and learned something new. If you have any questions or feedback, please leave a comment below.