c# - How to hide the current method from exception stack trace in .NET?

Question

I'd like to know if there is a way to throw an exception from inside a method, but to not include that method in the exception stack trace. E.g.

void ThrowSomeException()
{
    throw new SomeException();
}

And then, if I call that method from a method called Foo() I want the exception stack trace to start with at Foo(), not at ThrowSomeException(). I assume if this was possible it might be through the use of attributes on the method.

I'm interested in the general answer, but in case this isn't possible, what I'm really trying to do is create an extension method AssertEqual() for IEnumerable that I'll use in NUnit tests. So when I call myEnumerable.AssertEqual(otherEnumerable) and it fails, NUnit should report the error inside the test method, not inside the extension method.

Thanks!

Answer 1

Using the code at the end of this answer allows you to write code such as:

[HideFromStackTrace] // apply this to all methods you want omitted in stack traces
static void ThrowIfNull(object arg, string paramName)
{
    if (arg == null) throw new ArgumentNullException(paramName);
}

static void Foo(object something)
{
    ThrowIfNull(something, nameof(something));
    …
}

static void Main()
{
    try
    {
        Foo(null);
    }
    catch (Exception e)
    {
        Console.WriteLine(e.GetStackTraceWithoutHiddenMethods());
    }                  // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
}                      // gets a stack trace string representation
                       // that excludes all marked methods

Here's one possible implementation:

using System;
using System.Diagnostics;
using System.Linq;
using System.Reflection;

[AttributeUsage(AttributeTargets.Method, Inherited=false)]
public class HideFromStackTraceAttribute : Attribute { }

public static class MethodBaseExtensions
{
    public static bool ShouldHideFromStackTrace(this MethodBase method)
    {
        return method.IsDefined(typeof(HideFromStackTraceAttribute), true);
    }
}

public static class ExceptionExtensions
{
    public static string GetStackTraceWithoutHiddenMethods(this Exception e)
    {
        return string.Concat(
            new StackTrace(e, true)
                .GetFrames()
                .Where(frame => !frame.GetMethod().ShouldHideFromStackTrace())
                .Select(frame => new StackTrace(frame).ToString())
                .ToArray());  // ^^^^^^^^^^^^^^^     ^
    }                         // required because you want the usual stack trace
}                             // formatting; StackFrame.ToString() formats differently

Note that this only causes marked methods to be excluded from one particular representation of the stack trace, not from the stack trace itself. I know of no way to achieve the latter.

P.S.: If all you want is to hide a method in the Call Stack window during a debugging session, simply apply the [DebuggerHidden] attribute to the method.