How does the compiler handle interpolated strings without an expressions?
string output = $"Hello World";
Will it still try to format the string? How does the compiled code differ from that of one with an expression?
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1 Answer
For this C# code:
string output = $"Hello World";
int integer = 5;
string output2 = $"Hello World {integer}";
Console.WriteLine(output);
Console.WriteLine(output2);
I get this when I compile and then decompile (via ILSpy):
string value = "Hello World";
int num = 5;
string value2 = string.Format("Hello World {0}", num);
Console.WriteLine(value);
Console.WriteLine(value2);
So it seems that the compiler is smart enough not to use string.Format for the first case.
For completeness, here is the IL code:
IL_0000: nop
IL_0001: ldstr "Hello World"
IL_0006: stloc.0
IL_0007: ldc.i4.5
IL_0008: stloc.1
IL_0009: ldstr "Hello World {0}"
IL_000e: ldloc.1
IL_000f: box [mscorlib]System.Int32
IL_0014: call string [mscorlib]System.String::Format(string, object)
IL_0019: stloc.2
IL_001a: ldloc.0
IL_001b: call void [mscorlib]System.Console::WriteLine(string)
IL_0020: nop
IL_0021: ldloc.2
IL_0022: call void [mscorlib]System.Console::WriteLine(string)
IL_0027: nop
IL_0028: ret
It is clear here too that string.Format is only called for the second case.
1 Comment
roydukkey
Thanks. That's what I was hoping was happening.
