Implement `ToString()` on `System.Collections.DictionaryEntry`

[KirillOsenkov]

DictionaryEntry still doesn't have a good display in the debugger or when printing it to a log.

Could we implement ToString() that returns $"{Key} = {Value}", like KeyValurPair<TKey,TValue> has?

runtime/src/libraries/System.Private.CoreLib/src/System/Collections/Generic/KeyValuePair.cs

Line 46 in ae46d07

return KeyValuePair.PairToString(Key, Value);

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Issue Details

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DictionaryEntry still doesn't have a good display in the debugger or when printing it to a log.

Could we implement ToString() that returns $"{Key} = {Value}", like KeyValurPair<TKey,TValue> has?

runtime/src/libraries/System.Private.CoreLib/src/System/Collections/Generic/KeyValuePair.cs

Line 46 in ae46d07

return KeyValuePair.PairToString(Key, Value);

Author:	KirillOsenkov
Assignees:	-
Labels:	area-System.Collections, untriaged
Milestone:	-

[eiriktsarpalis]

So, should this be a change to how ToString() is implemented or would it make more sense to add a DebuggerDisplayAttribute?

[KirillOsenkov]

I'd prefer ToString() because there are several advantages:

• ToString() is useful in various other contexts, such as various text logs, format strings, interpolated strings, printf debugging, etc.
• KeyValuePair<TKey, TValue> uses ToString()
• compiler verifies correctness (vs. whatever you write in DebuggerDisplay is stringly typed)
• you can place a breakpoint in ToString()
• it's faster for the debugger (single eval call vs. interpreting the debugger display string)

[KirillOsenkov]

It's so frustrating when you see a useless type name in the logs for example, where it could have been meaningful and helpful to have the actual values.

[Joe4evr]

• compiler verifies correctness (vs. whatever you write in DebuggerDisplay is stringly typed)

Current preview can have compiler verification, tho:

[DebuggerDisplay($"{{{nameof(DebugDisplay)},nq}}")]
public class C
{
    private string DebugDisplay => ...;
}

[KirillOsenkov]

That's a good point, but unfortunately nobody writes it that way. Look at all existing DebuggerDisplay usages:
https://source.dot.net/#System.Private.CoreLib/DebuggerDisplayAttribute.cs,761078d4519dc54e,references

I just had to fix this recently because someone refactored code and forgot to update DebuggerDisplay:
https://github.com/dotnet/msbuild/pull/6650/files

[Joe4evr]

That's a good point, but unfortunately nobody writes it that way.

Only because the feature is new and nobody's used it yet. But at the very least, any new applications of DebuggerDisplay could (and I believe should) make use of the new feature so that mistakes like the one you linked can be spotted at compile-time.

[krwq]

@KirillOsenkov would you expect to add any string escaping into ToString? I'd expect to make it consistent with perhaps Tuple or other similar classes

[KirillOsenkov]

sure, anything is fine, ValueTuple, KVP, as long as it’s something.

[KirillOsenkov]

curious how ToString looks for anonymous types and old Tuples