Bug 13817 - BindingFlags.OptionalParamBinding behaves differently to .NET
Summary: BindingFlags.OptionalParamBinding behaves differently to .NET
Alias: None
Product: Class Libraries
Classification: Mono
Component: mscorlib ()
Version: unspecified
Hardware: PC Linux
: --- normal
Target Milestone: Untriaged
Assignee: Marek Safar
Depends on:
Reported: 2013-08-07 10:28 UTC by Piotr Zierhoffer
Modified: 2013-08-08 07:31 UTC (History)
4 users (show)

Is this bug a regression?: ---
Last known good build:

Source code presenting the problem. (470 bytes, text/x-csharp)
2013-08-07 10:28 UTC, Piotr Zierhoffer

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Description Piotr Zierhoffer 2013-08-07 10:28:14 UTC
Created attachment 4563 [details]
Source code presenting the problem.

Description of Problem:

According to the first comment from http://connect.microsoft.com/VisualStudio/feedback/details/521722/system-activator-createinstance-throws-system-missingmethodexception-with-constructor-containing-an-optional-parameter the attached code should invoke the constructor of A. It works on .NET (tested 3.5, 4.0, 4.5), but on Mono it throws MissingMethodException, due to the default parameter.

Steps to reproduce the problem:
1. Compile the code attached.
2. Run.

Actual Results:
MissingMethodException is thrown.

Expected Results:
"I'm alive!"

How often does this happen? 

Additional Information:
There are some differences in behaviour of Type.Missing in different .NET versions. Refer to the question I've asked on StackOverflow for details: http://stackoverflow.com/questions/18105825/bindingflags-optionalparameterbinding-varying-behaviour-in-different-frameworks
Comment 1 Piotr Zierhoffer 2013-08-07 13:37:54 UTC
According to Hans Passant's comment in the aforementioned stackoverflow question, this might be an implementation detail, while this usage of BindingFlags.OptionalParameterBinding is illegal (as stated in documentation). Tomorrow I'll try to verify a proper example.
Comment 2 Marek Safar 2013-08-08 07:31:40 UTC
Fixed in master