c# - 声明一个变量(作为新变量)然后初始化它和直接初始化它有什么区别？

Question

我见过人们使用几种不同的方式来初始化数组:

string[] Meal = new string[]{"Roast beef", "Salami", "Turkey", "Ham", "Pastrami"};

或者另一种方式，也称为初始化是:

string[] Meats = {"Roast beef", "Salami", "Turkey", "Ham", "Pastrami" };

什么是最好的方式，两种方式(包括内存分配)的主要区别是什么？

Answer 1

这两种情况没有区别。编译器生成相同的字节码(newarr OpCode):

public static void Main()
{
   string[] Meal = new string[] { "Roast beef", "Salami", "Turkey", "Ham", "Pastrami"};
   string[] Meats = { "Roast beef", "Salami", "Turkey", "Ham", "Pastrami" };
}

MSIL:

.entrypoint
  // Code size       100 (0x64)
  .maxstack  3
  .locals init ([0] string[] Meal,
           [1] string[] Meats,
           [2] string[] CS$0$0000)
  IL_0000:  nop
  IL_0001:  ldc.i4.5
  IL_0002:  newarr     [mscorlib]System.String
  IL_0007:  stloc.2
  IL_0008:  ldloc.2
  IL_0009:  ldc.i4.0
  IL_000a:  ldstr      "Roast beef"
  IL_000f:  stelem.ref
  IL_0010:  ldloc.2
  IL_0011:  ldc.i4.1
  IL_0012:  ldstr      "Salami"
  IL_0017:  stelem.ref
  IL_0018:  ldloc.2
  IL_0019:  ldc.i4.2
  IL_001a:  ldstr      "Turkey"
  IL_001f:  stelem.ref
  IL_0020:  ldloc.2
  IL_0021:  ldc.i4.3
  IL_0022:  ldstr      "Ham"
  IL_0027:  stelem.ref
  IL_0028:  ldloc.2
  IL_0029:  ldc.i4.4
  IL_002a:  ldstr      "Pastrami"
  IL_002f:  stelem.ref
  IL_0030:  ldloc.2
  IL_0031:  stloc.0
  IL_0032:  ldc.i4.5
  IL_0033:  newarr     [mscorlib]System.String
  IL_0038:  stloc.2
  IL_0039:  ldloc.2
  IL_003a:  ldc.i4.0
  IL_003b:  ldstr      "Roast beef"
  IL_0040:  stelem.ref
  IL_0041:  ldloc.2
  IL_0042:  ldc.i4.1
  IL_0043:  ldstr      "Salami"
  IL_0048:  stelem.ref
  IL_0049:  ldloc.2
  IL_004a:  ldc.i4.2
  IL_004b:  ldstr      "Turkey"
  IL_0050:  stelem.ref
  IL_0051:  ldloc.2
  IL_0052:  ldc.i4.3
  IL_0053:  ldstr      "Ham"
  IL_0058:  stelem.ref
  IL_0059:  ldloc.2
  IL_005a:  ldc.i4.4
  IL_005b:  ldstr      "Pastrami"
  IL_0060:  stelem.ref
  IL_0061:  ldloc.2
  IL_0062:  stloc.1
  IL_0063:  ret