Update AggregateException.xml

[epsitec]

Related to dotnet/runtime#107743

Summary

Fixes an incorrect description of what method GetBaseException() does.

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[jkotas]

Suggested change

	<summary>Returns the <see cref="T:System.Exception"/> that is the root cause of this exception. This exception is either the root exception or the first <see cref="T:System.AggregateException"/> that contains either multiple inner exceptions or no inner exceptions at all.</summary>
	<returns>The <see cref="T:System.Exception" /> that is the root cause of this exception.</returns>
	<summary>Returns the <see cref="T:System.AggregateException"/> that is the root cause of this exception. This exception is either the current exception or the first <see cref="T:System.AggregateException"/> that contains either multiple inner exceptions or no inner exceptions at all.</summary>
	<returns>The <see cref="T:System.AggregateException" /> that is the root cause of this exception.</returns>

https://learn.microsoft.com/en-us/dotnet/api/system.exception.getbaseexception and other docs use "current exception" for this.

Also, I think the original docs were better in highlighting that the returned instance is always AggregateException.

[epsitec]

The original docs were wrong, hence my fixes. The code will return the plain Exception which was thrown up the chain (what's now called the current exception), and only if there are multiple exceptions wrapped in an AggregateException will it return an aggregate exception. That's the whole point of this pull request.

[jkotas]

Ah ok, I have misread how the implementation behaves.

I agree with you that the return type in the docs is wrong.

I am not sure whether it makes sense to try to describe the exact algorithm used by this method in the docs. The current implementation of Exception.GetBaseException and AggregateException.GetBaseException methods are in conflict with the contract for these methods described in the docs.

https://learn.microsoft.com/en-us/dotnet/api/system.exception.getbaseexception?view=net-8.0 says "For all exceptions in a chain of exceptions, the GetBaseException method must return the same object (the base exception).". For example, this invariant does not seem to hold for

TargetInvocationException 
   -> AggregateException
          -> ArgumentException
          -> ArgumentException

GetBaseException() called on TargetInvocationException returns first ArgumentException for , but GetBaseException() called on AggregateException returns the same AggregateException.

We may want to fix the implementation and/or docs to make this more sensible.

[epsitec]

So, practically, are you @jkotas addressing this in the documentation?