CODEWITHSUNDEEP
c#genericstypestypeof
fearofawhackplanet
fearofawhackplanet

Reputation: 53388

Generic type paramaters are not types?

I find the following a bit confusing....

Dictionary<Type, Object> _typeMap;

public void RegisterType<T>(Object o)
{
    _typeMap.Add(typeof(T), o);
}

Why is typeof(T) required in the Add method? Isn't the T type paramater already a Type? What else is it?

Upvotes: 0

Views: 122

Answers (4)

Brian
Brian

Reputation: 951

This solution strikes me as a a bit of an "opps". I believe that the result of the this code will always be to try to add an entry with key "Type" into the dictionary due to the fact that you are always get the "typeof" of a Type. Instead I think what you are looking for is...

public void RegisterType<T>(Object o)
{
    _typeMap.Add(T, o);
}

Hope it helps!

Upvotes: -1

Amedio
Amedio

Reputation: 895

You hace to put the typeof(T) because T is the class definition, and the type is an object describing a Type, that for T and for Object and for String... etc etc.

typeof gets the Type of the class definition.

Upvotes: 0

Aliostad
Aliostad

Reputation: 81660

No. Add here needs an instance of a Type class.

Generic type parameters are not instances of Type class.

Upvotes: 1

Matti Virkkunen
Matti Virkkunen

Reputation: 65126

T is a type name, and typeof is used to retrieve the corresponding Type object.

A generic type parameter works exactly like just any other type name, say, int. You can't exactly do typeMap.Add(int, 0); either.

Upvotes: 6

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