When does a .net core exception filter get called after an exception is thrown?

Question

In my api I have a standard Controller containing an action, the action calls onto a service which then calls onto client to contact other third party api's.

I'm looking to implement an exception filter something similar to:

public class CustomExceptionFilterAttribute : ExceptionFilterAttribute
{
    private readonly IHostingEnvironment _hostingEnvironment;
    private readonly IModelMetadataProvider _modelMetadataProvider;

    public CustomExceptionFilterAttribute(
        IHostingEnvironment hostingEnvironment,
        IModelMetadataProvider modelMetadataProvider)
    {
        _hostingEnvironment = hostingEnvironment;
        _modelMetadataProvider = modelMetadataProvider;
    }

    public override void OnException(ExceptionContext context)
    {
        if (!_hostingEnvironment.IsDevelopment())
        {
            // do nothing
            return;
        }
        var result = new ViewResult {ViewName = "CustomError"};
        result.ViewData = new ViewDataDictionary(_modelMetadataProvider,context.ModelState);
        result.ViewData.Add("Exception", context.Exception);
        // TODO: Pass additional detailed data via ViewData
        context.Result = result;
    }
}

If my client class for example threw an exception would the filter get called immediately even though my service class which calls the client class had a try catch ready to catch such an exception?

I'll add the exact same code as linked in the question. I thought that was enough. — eVolve
I dont think it could be any clearer based off the last two lines in the question. — eVolve
please provide a minimal reproducible example. who is client? — Daniel A. White

Eric Munn Eric Munn · Accepted Answer · 2019-01-28T20:10:22

No. Per the documentation you refer to, the exception filter will only be triggered by unhandled exceptions; if the client exception is handled by the service and isn't rethrown, the exception filter will not fire.

Exception filters:

Don't have before and after events.

Implement OnException or OnExceptionAsync.

Handle unhandled exceptions that occur in controller creation, model binding, action filters, or action methods.

Do not catch exceptions that occur in Resource filters, Result filters, or MVC Result execution.

When does a .net core exception filter get called after an exception is thrown?

1 Answers