IPAddress.TryFormat returns false erroneously for shorter IP addresses

[stephentoub]

This:

char[] chars = new char[7];
Console.WriteLine(IPAddress.Parse("1.1.1.1").TryFormat(chars, out int charsWritten));
Console.WriteLine(charsWritten);

should print:

True
7

but instead it prints:

False
0

If the size of the char[] is increased to be at least 15, then it prints the desired output. The issue is the implementation is comparing the target destination buffer against the maximum size of a rendered IPv4 address, and failing if the destination is smaller than that.

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Issue Details

---

This:

char[] chars = new char[7];
Console.WriteLine(IPAddress.Parse("1.1.1.1").TryFormat(chars, out int charsWritten));
Console.WriteLine(charsWritten);

should print:

True
7

but instead it prints:

False
0

If the size of the char[] is increased to be at least 15, then it prints the desired output. The issue is the implementation is comparing the target destination buffer against the maximum size of a rendered IPv4 address, and failing if the destination is smaller than that.

Author:	stephentoub
Assignees:	stephentoub
Labels:	area-System.Net
Milestone:	8.0.0

[EgorBo]

Ouch, so e.g. google dns (8.8.8.8, 8.8.4.4) can't be parsed currently?

[stephentoub]

Ouch, so e.g. google dns (8.8.8.8, 8.8.4.4) can't be parsed currently?

It'll be parsed fine. It's just if you give a buffer smaller than 15 to TryFormat, TryFormat will return false. When whatever is formatting then grows the destination buffer to >= 15, it'll render fine.