IndexOf("\n") does not match "\r\n"

[gfs]

The string based IndexOf("\n") and LastIndexOf("\n") do not match Windows linebreaks (\r\n) but the character based IndexOf('\n') does. This contrasts with the behavior of Contains (and the apparent documented behavior of matching any substring) which matches \r\n for both Contains('\n') and Contains("\n").

Here's the output of IndexOf and LastIndexOf compared with Contains.

"\r\n".IndexOf("\n") = -1
"\r\n".IndexOf('\n') = 1
"\r\n".LastIndexOf("\n") = -1
"\r\n".LastIndexOf('\n') = 1
"\r\n".Contains("\n") = True
"\r\n".Contains('\n') = True

Code to demonstrate the issue.

using System;

namespace IndexOfDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            var inputstring = "\r\n";
            var printableInput = "\\r\\n";
            Console.WriteLine($"\"{printableInput}\".IndexOf(\"\\n\") = {inputstring.IndexOf("\n")}");
            Console.WriteLine($"\"{printableInput}\".IndexOf('\\n') = {inputstring.IndexOf('\n')}");
            Console.WriteLine($"\"{printableInput}\".LastIndexOf(\"\\n\") = {inputstring.LastIndexOf("\n")}");
            Console.WriteLine($"\"{printableInput}\".LastIndexOf('\\n') = {inputstring.LastIndexOf('\n')}");
            Console.WriteLine($"\"{printableInput}\".Contains(\"\\n\") = { inputstring.Contains("\n")}");
            Console.WriteLine($"\"{printableInput}\".Contains('\\n') = { inputstring.Contains('\n')}");
        }
    }
}

[ghost]

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Issue Details

---

The string based IndexOf("\n") and LastIndexOf("\n") do not match Windows linebreaks (\r\n) but the character based IndexOf('\n') does. This contrasts with the behavior of Contains (and the apparent documented behavior of matching any substring) which matches \r\n for both Contains('\n') and Contains("\n").

Here's the output of IndexOf and LastIndexOf compared with Contains.

"\r\n".IndexOf("\n") = -1
'\r\n'.IndexOf('\n') = 1
"\r\n".LastIndexOf("\n") = -1
'\r\n'.LastIndexOf('\n') = 1
"\r\n".Contains("\n") = True
'\r\n'.Contains('\n') = True

Code to demonstrate the issue.

using System;

namespace IndexOfDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            var inputstring = "\r\n";
            var printableInput = "\\r\\n";
            Console.WriteLine($"\"{printableInput}\".IndexOf(\"\\n\") = {inputstring.IndexOf("\n")}");
            Console.WriteLine($"'{printableInput}'.IndexOf('\\n') = {inputstring.IndexOf('\n')}");
            Console.WriteLine($"\"{printableInput}\".LastIndexOf(\"\\n\") = {inputstring.LastIndexOf("\n")}");
            Console.WriteLine($"'{printableInput}'.LastIndexOf('\\n') = {inputstring.LastIndexOf('\n')}");
            Console.WriteLine($"\"{printableInput}\".Contains(\"\\n\") = { inputstring.Contains("\n")}");
            Console.WriteLine($"'{printableInput}'.Contains('\\n') = { inputstring.Contains('\n')}");
        }
    }
}

Author:	gfs
Assignees:	-
Labels:	area-System.Globalization, untriaged
Milestone:	-

[tarekgh]

@gfs thanks for your report. This is a duplicate of #43736. Please have a look at the detailed discussion there and let's know of if you still have any question.