ExceptionHandler in c# WebAPI

Question

I have a question regarding how exactly this thing works.

public class GlobalExceptionHandler: ExceptionHandler
{
    private string _pvtMsg;

    public override void handle(ExceptionHandlerContext context)
    {
        //few if else conditions
        if()
        {
        }
        else if
        {
            _pvtMsg = "some value";
        }
        context.Result="Some random value depending upon if else execution";
    }
}

Now when _pvtMsg is set after that, whenever exception occurs it always have that same value as before.

Does, when I set _pvtMsg = "a"; in the else if condition, the next time an error occurs _pvtMsg still have value "a"?

Is there only a single instance of handler available throughout the lifespan of my application and hence this is happening? Or are there any other reasons? Any documents for reference would be appreciated.

Btw: this handler is registered with the Register method of the WebApiConfig.

config.Services.Replace(typeof(IExceptionHandler), new GlobalExceptionHandler());

Manfred Radlwimmer · Accepted Answer · 2016-05-18 09:49:27Z

3

Your assumption is correct. Since you register an Instance of GlobalExceptionHandler (with the new keyword) _pvrMsg will always have the value of the previous (successful) call.

If _pvrMsg is critical for whatever you are planning on doing in your if block, I'd recommend locking this part of the code to make sure handle doesn't execute multiple times at once.

The easiest way to do this would be:

public class GlobalExceptionHandler: ExceptionHandler
{
    private string _pvtMsg;
    private readonly object _lock = new object();

    public override void handle(ExceptionHandlerContext context)
    {
        lock(_lock)
        {
            //few if else conditions
            if()
            {
            }
            else if
            {
                _pvtMsg = "some value";
            }
            context.Result="Some random value depending upon if else execution";
        }
    }
}

edited May 18, 2016 at 9:49

answered May 18, 2016 at 9:43

Manfred Radlwimmer

13.4k13 gold badges55 silver badges65 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Mandy Over a year ago

Is there any other way to have new value for _pvtMsg for every exception? One way is I can reset the value during Handle method. but other than that is there any way?

Manfred Radlwimmer Over a year ago

The code is a bit empty, so I have no idea what you have planned for _pvtMsg.

Mandy Over a year ago

In _pvtMsg, I'm adding some custom message in specific exception cases. that's it.

Manfred Radlwimmer Over a year ago

No I mean, why do you need it when handler is called again? You could just use a local variable if you just want to store some text for context.Result.

Mandy Over a year ago

Yeah.. I guess that makes more sense :-) Thanks.

Collectives™ on Stack Overflow

ExceptionHandler in c# WebAPI

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related