Renaming C# entities using F2 shortcut opens a duplicate tab

[ghost]

Issue Type: Bug

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Steps to reproduce

1. Open a C# class in a .cs file.
2. Place cursor over the name of a class, method, or variable.
3. Press F2 to bring up the auto-rename prompt.
4. Type a different name in the auto-rename prompt and press enter.

Actual Result

A duplicate .cs file is opened in Visual Studio Code with the new name. The original tab remains but does not reflect the naming changes.

Expected Result

No duplicate tab is created. The original tab reflects the naming changes.

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VS Code version: Code 1.45.1 (5763d90, 2020-05-14T08:33:47.663Z)
OS version: Darwin x64 19.4.0

System Info

Item	Value
CPUs	Intel(R) Core(TM) i5-1030NG7 CPU @ 1.10GHz (8 x 1100)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled metal: disabled_off multiple_raster_threads: enabled_on oop_rasterization: disabled_off protected_video_decode: unavailable_off rasterization: enabled skia_renderer: disabled_off_ok video_decode: enabled viz_display_compositor: enabled_on viz_hit_test_surface_layer: disabled_off_ok webgl: enabled webgl2: enabled
Load (avg)	2, 2, 2
Memory (System)	16.00GB (3.41GB free)
Process Argv
Screen Reader	no
VM	0%

Extensions (6)

Extension	Author (truncated)	Version
csharp	ms-	1.21.18
remote-containers	ms-	0.117.1
remote-ssh	ms-	0.51.0
remote-ssh-edit	ms-	0.51.0
remote-wsl	ms-	0.44.2
vscode-remote-extensionpack	ms-	0.20.0

[ghost]

Update

It appears the issue is not exclusive to the F2 rename functionality. It is also happening with the Generate Method helper, accessible through CMD + . (CTRL + . in Windows).

[alexdima]

This appears to be a problem caused by the C# extension, perhaps they don't give good workspace edits.

[jrieken]

/extc#

[jrieken]

fyi @bpasero for the epic that discusses casing

[bpasero]

/duplicate #12448