How to create custom exceptions in .NET Core and when to consider doing so?

Question

Aryan Kumar · Answer

To create custom expectations in .NET Core, you can use the IAsyncExpectation interface. This interface provides a way to define custom expectations for asynchronous operations.

To create a custom expectation, you need to inherit from the IAsyncExpectation interface and implement the Handle method. The Handle method is called when the asynchronous operation is complete.

In the Handle method, you can check the outcome of the asynchronous operation and raise an error if the outcome is not as expected.

Here is an example of how to create a custom expectation that checks the status code of an HTTP response:

C#

public class StatusCodeExpectation : IAsyncExpectation
{
    private readonly int _expectedStatusCode;

    public StatusCodeExpectation(int expectedStatusCode)
    {
        _expectedStatusCode = expectedStatusCode;
    }

    public async Task Handle(CancellationToken cancellationToken)
    {
        var response = await Task.FromResult(null);

        if (response.StatusCode != _expectedStatusCode)
        {
            throw new Exception("Unexpected status code: " + response.StatusCode);
        }
    }
}

This custom expectation will check the status code of the HTTP response and raise an error if the status code is not equal to the expected status code.

You can consider creating custom expectations when you need to check the outcome of an asynchronous operation in a specific way. For example, you might need to check the status code of an HTTP response, or the value of a property in a JSON response.

Here are some additional things to consider when creating custom expectations:

The custom expectation should be reusable. You should be able to use the custom expectation in multiple places in your code.
The custom expectation should be easy to understand. The code for the custom expectation should be easy to read and understand.
The custom expectation should be efficient. The custom expectation should not add too much overhead to the asynchronous operation.

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How to create custom exceptions in .NET Core and when to consider doing so?

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