Скачать или смотреть Resolving Hangfire Background Job Creation Failed Due to InvalidCastException in ASP.NET Core

Discover how to fix the `InvalidCastException` encountered while using Hangfire in your ASP.NET Core project, ensuring smooth background job processing.
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Understanding the Hangfire Background Job Creation Error

When integrating Hangfire into your ASP.NET Core project, you may encounter an error that stops you from adding recurring or background jobs. This issue is often indicated by a specific exception message: Hangfire.BackgroundJobClientException: Background job creation failed. See inner exception for details. System.InvalidCastException: Unable to cast object of type 'System.Data.SqlClient.SqlConnection' to type 'Microsoft.Data.SqlClient.SqlConnection'. This guide will guide you through understanding this problem and provide a clear solution.

The Problem

In your .NET Core project, after setting up Hangfire to handle background jobs, you might experience the following:

Hangfire creates its database but throws an exception when trying to enqueue a job.

The exception specifically relates to an InvalidCastException indicating a type casting issue between System.Data.SqlClient and Microsoft.Data.SqlClient, which suggests a conflict between the libraries being used.

Here's a code snippet exhibiting a typical configuration that can lead to this issue:

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This issue often arises from using the wrong version of SQL client libraries. While System.Data.SqlClient is commonly used, Hangfire's storage options require specific version implementations that may conflict with your existing setup.

The Solution

Fortunately, you can resolve this InvalidCastException by updating your implementation to use the Microsoft.Data.SqlClient. Below is a step-by-step guide to fix the issue.

Step 1: Update Your Code

Change the line that configures your SQL Storage to create a new instance using Microsoft.Data.SqlClient.SqlConnection. Here’s what the updated part of your code would look like:

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Step 2: Add Necessary Packages

If you haven't done so already, ensure that you have the Microsoft.Data.SqlClient package installed. You can add it via NuGet Package Manager Console with the following command:

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Step 3: Test Your Configuration

After making the above changes, rebuild your project and run it again. You should be able to enqueue background jobs without encountering the previous InvalidCastException error.

Conclusion

Encountering casting issues like InvalidCastException when working with Hangfire can be frustrating, but by switching to Microsoft.Data.SqlClient for your database connections, you can resolve the problem efficiently. Always ensure to look closely at the assembly requirements and dependencies when configuring libraries in your projects, as they can conflict in unexpected ways. By following the steps laid out in this guide, you can ensure a smoother experience when working with Hangfire in ASP.NET Core.

If you have more questions or need further assistance, feel free to leave your thoughts in the comments!