Indexers in List vs Array

Question

How are the Indexers are defined in List and Arrays.

List lists=new List(); where MyStruct is a Structure.

Answer 1

List has a normal indexer which behaves like a property. The access goes through accessor functions, and those are by-value.

T this[int index]
{
    get{return arr[index];}
    set{arr[index]=value;}}
}

Arrays are special types, and their indexer is field-like. Both the runtime and the C# compiler have special knowledge of arrays, and that enables this behavior. You can't have the array like behavior on custom types.

Fortunately this is rarely a problem in practice. Since you only use mutable structs in rare special cases(high performance or native interop), and in those you usually prefer arrays anyways due to their low overhead.

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You get the same behavior with properties vs. fields. You get a kind of reference when using a field, but a copy when you use a property. Thus you can write to members of value-type fields, but not members of value-type properties.