C#•4y ago

✅ Explicit call ToString() when interpolating on primitive (value) types

Is it necessary to call ToString() when interpolating string using primitive (int, float, etc.) or in general value types?
Would it avoid boxing allocation?

Example:

int someInt = 4;
MyStructWithImplementedInterfaceIFormatable myStruct;
Console.Write($"My number is: {someInt.ToString()} and struct: {myStruct.ToString()}");

int someInt = 4;
MyStructWithImplementedInterfaceIFormatable myStruct;
Console.Write($"My number is: {someInt.ToString()} and struct: {myStruct.ToString()}");

ero•12/12/22, 8:44 AM

Well first off this doesn't compile. But also, why not just try it?

MODiX•12/12/22, 8:45 AM

Ero#1111

REPL Result: Success

Console Output

Compile: 606.991ms | Execution: 32.196ms | React with ❌ to remove this embed.

IceTrooper 🧊OP•12/12/22, 8:46 AM

What do you want to explain to me? ;p
I know it would work, but the essence of the question is: should I call explicitlly ToString to avoid boxing allocation?

ero•12/12/22, 8:46 AM

You asked 2 separate questions

ero•12/12/22, 8:46 AM

Not my fault

Eero You asked 2 separate questions

IceTrooper 🧊OP•12/12/22, 8:48 AM

Ok, I'm sorry. You're right that it could be understood this way

ero•12/12/22, 8:50 AM

Calling ToString on anything will allocate (a string), i dont think it would box?

Eero Calling ToString on anything will allocate (a string), i dont think it would box...

IceTrooper 🧊OP•12/12/22, 9:00 AM

Yeah, but here I'm using value types

IIceTrooper 🧊Is it necessary to call ToString() when interpolating string using primitive (in...

Thinker•12/12/22, 9:15 AM

is called implicitly when using string interpolation

Thinker•12/12/22, 9:16 AM

It will allocate a string regardless (I think)

TThinker `.ToString()` is called implicitly when using string interpolation

IceTrooper 🧊OP•12/12/22, 9:18 AM

Yes, but on what type is it called implicitly?
On int/MyStruct directly or is it boxing value type to and then it will call ToString() (less efficient)?

Thinker•12/12/22, 9:20 AM

The IL contains no boxing, although you might have to dig into the source of .

MODiX•12/12/22, 9:20 AM

thinker227#5176

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TThinker The IL contains no boxing, although you might have to dig into the source of `De...

IceTrooper 🧊OP•12/12/22, 9:26 AM

Yeah, I also checked that it uses that handler, but I cannot find information how it behaves internally. :/

Thinker•12/12/22, 9:28 AM

The source is here
https://source.dot.net/#System.Private.CoreLib/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/DefaultInterpolatedStringHandler.cs,1aa9a7f847d81b2f

Thinker•12/12/22, 9:28 AM

It has some pretty extensive comments if you wanna read through it

Thinker•12/12/22, 9:30 AM

It appears that when formatting objects, it tries to format it using , otherwise it calls on the type.

Thinker•12/12/22, 9:31 AM

However it's using a type argument, which means that no boxing is taking place.

MODiX•12/12/22, 9:39 AM

Retax#0813

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IceTrooper 🧊OP•12/12/22, 9:54 AM

Thinker

@Retax
I was just reading links you pasted and articles about that. Do I understand correctly that since C#10 we got a concept of String Interpolation Handlers and it's optimized on that level so we don't have to explicitly call ToString() on value-types?
https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/tutorials/interpolated-string-handler

Unlike previous versions of C#, where string.Format was used when calling interpolation with int (without explicitly ToString() call).
https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/proposals/csharp-10.0/improved-interpolated-strings#the-handler-pattern

IceTrooper 🧊OP•12/12/22, 9:56 AM

Last sum up question:
Does it follow that up to C#10 version you should call ToString() yourself, but since this version they have improved it and DefaultInterpolatedStringHandler does it for us?

Original message was deleted

IceTrooper 🧊OP•12/12/22, 10:26 AM

I think I'm going to disagree with that. Can you justify it?

As far as I can see in the latest version of C# we use a generic method that checks if the type implements the IFormatable interface.
However, the old C# uses the string.Format(string, object) method, so he is already doing the boxing allocation at the stage of calling this method. Calling ToString() by itself gets rid of this.

IceTrooper 🧊OP•12/12/22, 10:27 AM

https://sharplab.io/#v2:EYLgZgpghgLgrgJwgZwLQBsD2BjK7VhwB22MAlpkarDAmcHDCgDQwhnrMAmIA1AD4ABAEwBGALAAoQQGYABCLkBhOQG8pczQvmCALHICyACgCUajVstkiMOQFsAngEkbcgLxzdAbguXNvv0FRAAY5AGtRdzkAEgAiAwc5azY1RxcYAF9Yn0k/LQCrV0cAZQhsSi50qIBWHLz/XPri2msAc3DhKLiEuWQyiqSbEFSHUvKiSpsAOgAVTGa6IlbTLLqtDKkMoA=

Original message was deleted

IceTrooper 🧊OP•12/12/22, 12:29 PM

Thank you

Accord•12/13/22, 12:41 PM

Was this issue resolved? If so, run

/close

/close

otherwise I will mark this as stale and this post will be archived until there is new activity.