Add index to OrderedDictionary debugger display

[Copilot]

Changed OrderedDictionary debugger display to use a list-style view where items are shown as KeyValuePairs with implicit indexing from array position. The debugger will display:

[0] = {["One", "1"]}
[1] = {["Two", "2"]}

Changes Made

• OrderedDictionaryDebugView.cs: New custom debugger type proxy that returns a KeyValuePair<TKey, TValue>[] array. Simplified implementation uses CopyTo for better performance.
• OrderedDictionary.cs: Updated DebuggerTypeProxy attribute to always use OrderedDictionaryDebugView
• System.Collections.csproj: Added new debug view file to compilation
• System.Text.Json.csproj: Added OrderedDictionaryDebugView.cs as a polyfill to ensure consistent debug view behavior across all projects that compile OrderedDictionary internally
• DebugView.Tests.cs:
  • Added OrderedDictionary to list-style tests with string keys ("One", "Two") to distinguish array indices [0], [1] from dictionary keys
  • Added dedicated test TestDebuggerAttributes_OrderedDictionary that validates the debug view returns KeyValuePair array items in the correct order
  • Wrapped OrderedDictionary test cases with #if !NETFRAMEWORK to prevent compilation errors on .NET Framework where the type is not available

The list-style view shows index information implicitly through array position ([0], [1], [2]) while keeping the key/value relationship clear with standard KeyValuePair display. This matches the display pattern used by Queue, Stack, and List.

Testing

• ✅ All 3,782 OrderedDictionary tests pass
• ✅ All DebugView tests pass (including new dedicated test)
• ✅ System.Collections builds successfully
• ✅ System.Text.Json builds successfully (all target frameworks)
• ✅ CodeQL security analysis: No issues found
• ✅ Fixed .NET Framework build errors

Fixes #118590

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add index to debugging display of OrderedDictionary<TKey, TValue></issue_title>
<issue_description>Since .NET 9 the new display info for dictionaries is [KEY, VALUE] coming from previous [INDEX, KEY/VALUE].

But index information is important here, so please add index => [INDEX/KEY, VALUE].</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #118590

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[stephentoub]

@copilot:

Build FAILED.

D:\a\_work\1\s\src\libraries\System.Collections\src\System\Collections\Generic\OrderedDictionary.cs(26,31): error CS0246: The type or namespace name 'OrderedDictionaryDebugView<,>' could not be found (are you missing a using directive or an assembly reference?) [D:\a\_work\1\s\src\libraries\System.Text.Json\src\System.Text.Json.csproj::TargetFramework=netstandard2.0]
    0 Warning(s)
    1 Error(s)

[Copilot]

@copilot:

Build FAILED.

...

Fixed build error by making the DebuggerTypeProxy attribute conditional. When SYSTEM_COLLECTIONS is defined (System.Collections project), it uses OrderedDictionaryDebugView. Otherwise (e.g., System.Text.Json for netstandard2.0), it falls back to IDictionaryDebugView.

Commit: TBD (in progress)

[eiriktsarpalis]

@copilot could you add back testing that validates the expected display format?

[Copilot]

@copilot could you add back testing that validates the expected display format?

Added TestDebuggerAttributes_OrderedDictionary test that validates the debug view returns KeyValuePair array items in the correct order. The test confirms that OrderedDictionary displays as a list of KeyValuePairs with implicit indexing from array position.

Commit: TBD (in progress)

[eiriktsarpalis]

@copilot please fix the failing builds

[Copilot]

@copilot please fix the failing builds

I've verified that both System.Collections and System.Text.Json build successfully locally, and the ./build.sh libs command also succeeds. Could you provide the specific error messages or logs from the failing builds so I can identify and fix the issue?

[eiriktsarpalis]

@copilot take a look at CI logs:

D:\a\_work\1\s\src\libraries\Common\tests\System\Collections\DebugView.Tests.cs(169,45): error CS0246: The type or namespace name 'OrderedDictionary<,>' could not be found (are you missing a using directive or an assembly reference?) [D:\a\_work\1\s\src\libraries\System.Collections.Immutable\tests\System.Collections.Immutable.Tests.csproj::TargetFramework=net481]
##[error]src\libraries\Common\tests\System\Collections\DebugView.Tests.cs(169,45): error CS0246: (NETCORE_ENGINEERING_TELEMETRY=Build) The type or namespace name 'OrderedDictionary<,>' could not be found (are you missing a using directive or an assembly reference?)
D:\a\_work\1\s\src\libraries\Common\tests\System\Collections\DebugView.Tests.cs(197,45): error CS0246: The type or namespace name 'OrderedDictionary<,>' could not be found (are you missing a using directive or an assembly reference?) [D:\a\_work\1\s\src\libraries\System.Collections.Immutable\tests\System.Collections.Immutable.Tests.csproj::TargetFramework=net481]
##[error]src\libraries\Common\tests\System\Collections\DebugView.Tests.cs(197,45): error CS0246: (NETCORE_ENGINEERING_TELEMETRY=Build) The type or namespace name 'OrderedDictionary<,>' could not be found (are you missing a using directive or an assembly reference?)
D:\a\_work\1\s\src\libraries\Common\tests\System\Collections\DebugView.Tests.cs(287,28): error CS0246: The type or namespace name 'OrderedDictionary<,>' could not be found (are you missing a using directive or an assembly reference?) [D:\a\_work\1\s\src\libraries\System.Collections.Immutable\tests\System.Collections.Immutable.Tests.csproj::TargetFramework=net481]
##[error]src\libraries\Common\tests\System\Collections\DebugView.Tests.cs(287,28): error CS0246: (NETCORE_ENGINEERING_TELEMETRY=Build) The type or namespace name 'OrderedDictionary<,>' could not be found (are you missing a using directive or an assembly reference?)

[Copilot]

@copilot take a look at CI logs:

...

Fixed by wrapping OrderedDictionary test cases with #if !NETFRAMEWORK since OrderedDictionary<TKey, TValue> is not available in .NET Framework.

Commit: TBD (in progress)

[stephentoub]

@eiriktsarpalis, my sign-off doesn't count; can you review?

[tarekgh]

@eiriktsarpalis, my sign-off doesn't count; can you review?

I signed off, I think @eiriktsarpalis is not available today.

[eiriktsarpalis]

/ba-g test failures unrelated.