how to cmpare same types where IsGenericTypeDefinition is deff

Question

I have a issue where I want to identify if a object is of type KeyValuePair<,>

when I compare in if:

else if (item.GetType() == typeof(KeyValuePair<,>))
{
    var key = item.GetType().GetProperty("Key");
    var value = item.GetType().GetProperty("Value");
    var keyObj = key.GetValue(item, null);
    var valueObj = value.GetValue(item, null);
    ...
}

this is false as IsGenericTypeDefinition is different for them.

Can someone explain me why this is happening and how to solve the this issue in correct way (I mean not comparing Names or other trivial fields.)

THX in advance!

Answer 1

item.GetType() == typeof(KeyValuePair<,>)

The above will never work: it is impossible to make an object of type KeyValuePair<,>.

The reason is that typeof(KeyValuePair<,>) does not represent a type. Rather, it is a generic type definition - a System.Type object used to examine structures of other generic types, but not themselves representing a valid .NET type.

If an item is, say, a KeyValuePair<string,int>, then item.GetGenericTypeDefintion() == typeof(KeyValuePair<,>)

Here is how you can modify your code:

...
else if (item.IsGenericType() && item.GetGenericTypeDefintion() == typeof(KeyValuePair<,>)) {
    ...
}

Answer 2

Found this piece of code, give it a try:

public bool IsKeyValuePair(object o) 
{
    Type type = o.GetType();

    if (type.IsGenericType)
    {
        return type.GetGenericTypeDefinition() != null ? type.GetGenericTypeDefinition() == typeof(KeyValuePair<,>) : false;
    }

    return false;
}

Source:

http://social.msdn.microsoft.com/Forums/hu-HU/csharpgeneral/thread/9ad76a19-ed9c-4a02-be6b-95870af0e10b