In C# what is the meaning of 1 after IEnumerable in System.Collections.Generic.IEnumerable`1

Question

在IEnumerable之后1的含义是什么： System.Collections.Generic.IEnumerable`1

Answer 1

It is the generic arity of the type, or put another way, the number of type parameters a generic type supports. IEnumerable<T> supports a single type parameter. If you were to look at Dictionary<TKey, TValue> you would notice an arity value of 2.

Answer 2

Within the .NET type system, it is necessary that types have unique names. Although it is only possible to create instances of bound generic types (eg IEnumerable<System.Int32> or IEnumerable<System.String> ), the unbound generic type may be used in certain contexts. Within the language C#, such type would be written as IEnumerable<> but within the type system it is notated as IEnumerable~1 [~ used to avoid format problems]. Note that the name of the bound generic type starts with the name of the unbound type, so if the unbound generic were called IEnumerable<> within the type system, the name of the bound generic would have to start with IEnumerable<> , including the back-to-back less-than-greater-than signs .