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copied!<p>If we take a look at the jitted code, we'll see that <code>str2</code> is assembled using <code>String.Concat</code> and that it in fact is not the same reference as <code>str1</code>. We will also see that the comparison is done using <code>Equals</code>. In other words the assert passes as the strings contain the same characters. </p> <p>This code</p> <pre><code>static void Main(string[] args) { string str1 = "foofoo"; string strFoo = "foo"; string str2 = strFoo + strFoo; Console.WriteLine(str1 == str2); Debugger.Break(); } </code></pre> <p>is jitted to (please scroll sideways to see comments)</p> <pre><code>C:\dev\sandbox\cs-console\Program.cs @ 22: 00340070 55 push ebp 00340071 8bec mov ebp,esp 00340073 56 push esi 00340074 8b3530206003 mov esi,dword ptr ds:[3602030h] ("foofoo") <-- Note address of "foofoo" C:\dev\sandbox\cs-console\Program.cs @ 23: 0034007a 8b0d34206003 mov ecx,dword ptr ds:[3602034h] ("foo") <-- Note different address for "foo" C:\dev\sandbox\cs-console\Program.cs @ 24: 00340080 8bd1 mov edx,ecx 00340082 e81977fe6c call mscorlib_ni+0x2b77a0 (6d3277a0) (System.String.Concat(System.String, System.String), mdToken: 0600035f) <-- Call String.Concat to assemble str2 00340087 8bd0 mov edx,eax 00340089 8bce mov ecx,esi 0034008b e870ebfd6c call mscorlib_ni+0x2aec00 (6d31ec00) (System.String.Equals(System.String, System.String), mdToken: 060002d2) <-- Compare using String.Equals 00340090 0fb6f0 movzx esi,al 00340093 e83870f86c call mscorlib_ni+0x2570d0 (6d2c70d0) (System.Console.get_Out(), mdToken: 060008fd) 00340098 8bc8 mov ecx,eax 0034009a 8bd6 mov edx,esi 0034009c 8b01 mov eax,dword ptr [ecx] 0034009e 8b4038 mov eax,dword ptr [eax+38h] 003400a1 ff5010 call dword ptr [eax+10h] C:\dev\sandbox\cs-console\Program.cs @ 28: 003400a4 e87775596d call mscorlib_ni+0x867620 (6d8d7620) (System.Diagnostics.Debugger.Break(), mdToken: 0600239a) C:\dev\sandbox\cs-console\Program.cs @ 29: >>> 003400a9 5e pop esi 003400aa 5d pop ebp 003400ab c3 ret </code></pre>

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