Question

I needed to serialize KeyValuePair and I found the solution here:

Is there a serializable generic Key/Value pair class in .NET?

So I used the accepted answer for that question which said all you need is to define class/struct like this

public class KeyValuePair<K,V>
{
  public K Key {get;set;}
  public V Value {get;set;}
}

This works but now there are 2 generic classes with same name. The custom class above and the one from System.Collections.Generics namespace.

So how does the compiler know which one to use when there is a code like this

myList=new List<KeyValuePair<string, string>>();

One has signature KeyValuePair<K,V> and the other is KeyValuePair<TKey,TValue>, so both have same number of Type Parameters.

Why does the code compile with no errors?

Answer 1

Name, namespace an generic type parameters are unique per assembly. Nothing prevents you from creating another type like you do it, but the compiler will not be able to figure out which one to use if yet another project uses both assemblies (the system one and yours).

Another variant of the same problem occurs when two same assemblies with different versions are in use, the compiler will pick and bind to one which can cause painful a debugging experience (it looks as if the types shoud match but they don’t – the framework itself has no problem with it though).

Note that you cannot replace a type in another assembly by “redefining” is like this.