Inspecting double.ToString()

Question

As a follow up to a question I had about optimising the conversion of double to string for memory (see c# double to character array or alternative) I wanted to see how double.ToString() is implemented under the hood in .NET. When I use ildasm or DotPeek i get as far as:

[SecurityCritical]
[MethodImpl(MethodImplOptions.InternalCall)]
public static string FormatDouble(double value, string format, NumberFormatInfo info);

or

IL_0008:  call string System.Number::FormatDouble(float64,
                                                  string,
                                                  class System.Globalization.NumberFormatInfo)

And can't drill further. I think if my understanding is right it's because this is a call into the CLR. I wanted to know is there any easy way to find out what the implementation is?

score 3 · Answer 1 · answered Jun 07 '12 at 09:00

3

What about looking at mono source code? Mono simply use IL to do the whole thing without any C code.

mcs/class/corlib/System/Double.cs
mcs/class/corlib/System/NumberFormatter.cs

answered Jun 07 '12 at 09:00

linquize

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score 3 · Accepted Answer · answered Sep 11 '17 at 07:34

Since .NET Core is open source now, answer to this question can be updated. MethodImplOptions.InternalCall indicates FormatDouble is a FCall, which is a mechanism of communicating to native implementation. You can find the native implementation of FormatDouble here.

score 1 · Answer 3 · answered Jun 07 '12 at 09:00

1

I think WinDbg would be helpful - and did you checkout the implementation in mono?

answered Jun 07 '12 at 09:00

Jeffrey Zhao

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score 0 · Answer 4 · answered Apr 13 '21 at 08:57

0

In .NET 5, FormatDouble is now implemented in C#, the source code is available in the dotnet/runtime repository.

answered Apr 13 '21 at 08:57

pogosama

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Inspecting double.ToString()

4 Answers4