c# – 在字典初始值设定项中使用方括号和花括号之间有区别吗？

new Dictionary<string, GradientSpace>
{
    ["userSpaceOnUse"] = GradientSpace.Absolute,
    ["objectBoundingBox"] = GradientSpace.Relative
})

和

new Dictionary<string, GradientSpace>
{
    {"userSpaceOnUse", GradientSpace.Absolute},
    {"objectBoundingBox", GradientSpace.Relative}
});

在这两种语法中是否存在任何差异,或者仅仅是偏好问题？

var x = new Dictionary<string, int>
{
    ["userSpaceOnUse"] = 1,
    ["objectBoundingBox"] = 3
};

var y = new Dictionary<string, int> {
    {"userSpaceOnUse", 1},
    {"objectBoundingBox", 3}
};

这导致以下中间语言(使用JetBrains dotPeek)：

// [18 13 - 22 15]
IL_0001: newobj       instance void class [mscorlib]System.Collections.Generic.Dictionary`2<string, int32>::.ctor()
IL_0006: dup          
IL_0007: ldstr        "userSpaceOnUse"
IL_000c: ldc.i4.1     
IL_000d: callvirt     instance void class [mscorlib]System.Collections.Generic.Dictionary`2<string, int32>::set_Item(!0/*string*/, !1/*int32*/)
IL_0012: nop          
IL_0013: dup          
IL_0014: ldstr        "objectBoundingBox"
IL_0019: ldc.i4.3     
IL_001a: callvirt     instance void class [mscorlib]System.Collections.Generic.Dictionary`2<string, int32>::set_Item(!0/*string*/, !1/*int32*/)
IL_001f: nop          
IL_0020: stloc.0      // x

// [25 13 - 28 15]
IL_0021: newobj       instance void class [mscorlib]System.Collections.Generic.Dictionary`2<string, int32>::.ctor()
IL_0026: dup          
IL_0027: ldstr        "userSpaceOnUse"
IL_002c: ldc.i4.1     
IL_002d: callvirt     instance void class [mscorlib]System.Collections.Generic.Dictionary`2<string, int32>::Add(!0/*string*/, !1/*int32*/)
IL_0032: nop          
IL_0033: dup          
IL_0034: ldstr        "objectBoundingBox"
IL_0039: ldc.i4.3     
IL_003a: callvirt     instance void class [mscorlib]System.Collections.Generic.Dictionary`2<string, int32>::Add(!0/*string*/, !1/*int32*/)
IL_003f: nop          
IL_0040: stloc.1      // y

第一种方法导致设置索引器/属性,而第二种方式使用Add()方法,这意味着它们的翻译方式不同.

在这种情况下,Dictionarry类的.NET Core源也很有趣：
https://github.com/Microsoft/referencesource/blob/master/mscorlib/system/collections/generic/dictionary.cs