Applying '==' operator to generic parameter

Question

Possible Duplicate:
Can’t operator == be applied to generic types in C#?

I have a DatabaseLookup{} class where the parameter T will be used by the lookup methods in the class. Before lookup, I want to see if T was already looked up with something like

if (T == previousLookupObject) ...

This doesn't compile at all. What is preventing me from making a simple comparison like this?

Is `T` referring to the generic type or an actual variable of the generic. `T` is usually used as the name of the generic type. Not an object but a type. Try defining a variable of type `T`. — Chad La Guardia, Apr 15 '11 at 21:21
And then use `thisObject.Equals(previousLookupObject)` instead of `==` — H H, Apr 15 '11 at 21:26

score 16 · Accepted Answer · answered Apr 15 '11 at 21:22

T is the type parameter. If your previousLookupObject is an object of Type, you need to do typeof(T) == previousLookupObject.

If previousLookupObject is variable of type T, you need to have an actual object of T to compare it to.

If you want to find out if previousLookupObject is of type T, you need to use the is operator: if (previousLookupObject is T).

score 8 · Answer 2 · answered Apr 15 '11 at 21:22

8

T is type, previousLookupObject is (I suppose) an object instance. So you are comparing apples to oranges. Try this:

if (previousLookupObject is T)
{
    ...    
}

answered Apr 15 '11 at 21:22

Darin Dimitrov

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score 1 · Answer 3 · edited May 23 '17 at 10:33

1

Refer to the following links:

Can't operator == be applied to generic types in C#?

c# compare two generic values

edited May 23 '17 at 10:33

Community

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answered Apr 15 '11 at 21:29

Akram Shahda

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score 0 · Answer 4 · answered Apr 15 '11 at 21:22

0

What type is previousLookupObject? Generic type parameters are types, and can't be used as normal object references.

answered Apr 15 '11 at 21:22

recursive

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Applying '==' operator to generic parameter

4 Answers4