ExpressionHelper contains a compatibility bug with Roslyn compiler

[doggy8088]

There is a bug in the ASP.NET MVC 5.2.3 for a long time. It's hard to explain this in English. So I made a few steps to reproduce this problem.

STEPS TO REPRODUCE THE PROBLEM

1. Create a simple ASP.NET MVC 5 project using Visual Studio 2017
2. Apply change to the follow code snippets. Only 3 files to change.
   https://gist.github.com/doggy8088/58dd3c773ef9877155b19ebb2fda8525
3. Start debugging and navigate to /Home/Index page. Then you will see the result like below:
   
   As you can see, the @Html.TextBoxFor(m => data[i].Name) generated field name in the for-loop in the view are all wrong.

MORE INFO

This problem is only exists when ASP.NET MVC 5 project using Roslyn to compiler views.

I was wrote an article about 2 years ago. My article is written in Chinse. If some of you can read Chinese, you can also reference my article over here: https://blog.miniasp.com/post/2016/03/06/ASPNET-MVC-5-View-Roslyn-problem-workaround.aspx

I actually proposed a pull request to fix this problem about 2 years ago too. You may check it out too.

[mkArtakMSFT]

@dougbu, can you please look into this?

[mkArtakMSFT]

Thanks for contacting us. One of our team members will look into it and get back to you.

[IanKemp]

tl;dr backporting the fixes from this commit in ASP.NET Core MVC should resolve the issue.

[doggy8088]

@mkArtakMSFT Any new progress on this issue?

[mkArtakMSFT]

@dougbu, did you get a chance to look into this?

[dougbu]

@mkArtakMSFT I read the comments over the weekend and no longer think we need an investigation.

We fixed a related problem in ASP.NET Core and can do something similar here. That should fix the problem. Should however spend some time adding a number of tests covering more-complicated lambda expressions in this repo.

BTW, I'm surprised Roslyn versions are material here: I would expect the set of captured local variables to remain fairly consistent.

[dougbu]

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