When I compile this code with mono (gmcs) and run it, it outputs -1 (both with mono and .Net framework). When I compile it with VS (csc), it outputs -1 when I run it with mono, and 0 when I run it with the .Net framework.

The code in question is:

using System;

public class Program {
    public static void Main() {
        Console.WriteLine(string.Compare("alo\0alo\0", "alo\0alo\0\0", false, System.Globalization.CultureInfo.InvariantCulture));
    }
}

Compiled with VS:

.method public hidebysig static void  Main() cil managed
{
  .entrypoint
  // Code size       29 (0x1d)
  .maxstack  8
  IL_0000:  nop
  IL_0001:  ldstr      bytearray (61 00 6C 00 6F 00 00 00 61 00 6C 00 6F 00 00 00 ) // a.l.o...a.l.o...
  IL_0006:  ldstr      bytearray (61 00 6C 00 6F 00 00 00 61 00 6C 00 6F 00 00 00   // a.l.o...a.l.o...
                                  00 00 ) 
  IL_000b:  ldc.i4.0
  IL_000c:  call       class [mscorlib]System.Globalization.CultureInfo [mscorlib]System.Globalization.CultureInfo::get_InvariantCulture()
  IL_0011:  call       int32 [mscorlib]System.String::Compare(string,
                                                              string,
                                                              bool,
                                                              class [mscorlib]System.Globalization.CultureInfo)
  IL_0016:  call       void [mscorlib]System.Console::WriteLine(int32)
  IL_001b:  nop
  IL_001c:  ret
} // end of method Program::Main

Compiled with mono:

.method public hidebysig static void  Main() cil managed
{
  .entrypoint
  // Code size       27 (0x1b)
  .maxstack  8
  IL_0000:  ldstr      bytearray (61 00 6C 00 6F 00 00 00 61 00 6C 00 6F 00 00 00 ) // a.l.o...a.l.o...
  IL_0005:  ldstr      bytearray (61 00 6C 00 6F 00 00 00 61 00 6C 00 6F 00 00 00   // a.l.o...a.l.o...
                                  00 00 ) 
  IL_000a:  ldc.i4.0
  IL_000b:  call       class [mscorlib]System.Globalization.CultureInfo [mscorlib]System.Globalization.CultureInfo::get_InvariantCulture()
  IL_0010:  call       int32 [mscorlib]System.String::Compare(string,
                                                              string,
                                                              bool,
                                                              class [mscorlib]System.Globalization.CultureInfo)
  IL_0015:  call       void [mscorlib]System.Console::WriteLine(int32)
  IL_001a:  ret
} // end of method Program::Main

The only difference is the two extra NOP instructions in the VS version.

How is it possible?