You can't create immutable collection with a collection initializer because the compiler translates them into a sequence of calls to the Add
method. For example if you look at the IL code for var d = new Dictionary<string, int> { { "a", 1 }, { "b", 2 } };
you'll get
IL_0000: newobj instance void class [mscorlib]System.Collections.Generic.Dictionary`2<string, int32>::.ctor()
IL_0005: dup
IL_0006: ldstr "a"
IL_000b: ldc.i4.1
IL_000c: callvirt instance void class [mscorlib]System.Collections.Generic.Dictionary`2<string, int32>::Add(!0, !1)
IL_0011: dup
IL_0012: ldstr "b"
IL_0017: ldc.i4.2
IL_0018: callvirt instance void class [mscorlib]System.Collections.Generic.Dictionary`2<string, int32>::Add(!0, !1)
Obviously this violates the concept of immutable collections.
Both your own answer and Jon Skeet's are ways to deal with this.
// lukasLansky's solution
var d = new Dictionary<string, int> { { "a", 1 }, { "b", 2 } }.ToImmutableDictionary();
// Jon Skeet's solution
var builder = ImmutableDictionary.CreateBuilder<string, int>();
builder.Add("a", 1);
builder.Add("b", 2);
var result = builder.ToImmutable();
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…