没有表达式的 C# 字符串插值如何编译?

How does C# string interpolation without an expression compile?

编译器如何处理没有表达式的内插字符串?

string output = $"Hello World";

它还会尝试格式化字符串吗?编译后的代码与带有表达式的代码有何不同?

对于此 C# 代码:

string output = $"Hello World";

int integer = 5;

string output2 = $"Hello World {integer}";

Console.WriteLine(output);

Console.WriteLine(output2);

我在编译然后反编译(通过 ILSpy)时得到这个:

string value = "Hello World";
int num = 5;
string value2 = string.Format("Hello World {0}", num);
Console.WriteLine(value);
Console.WriteLine(value2);

所以看起来编译器足够聪明,不会在第一种情况下使用 string.Format

为了完整起见,这里是 IL 代码:

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

这里也很清楚,string.Format只是在第二种情况下被调用。