Check if 'T' inherits or implements a class/interface

Question

Is there a way to test if T inherits/implements a class/interface?

private void MyGenericClass ()
{
    if(T ... inherits or implements some class/i         


        

Answer 1

Alternate ways to tell if an object o inherits a class or implements an interface is to use the is and as operators.

If you want to only know if an object inherits a class or implements an interface, the is operator will return a boolean result:

bool isCompatibleType = (o is BaseType || o is IInterface);

If you want to use the inherited class or implemented interface after your test, the as operator will perform a safe cast, returning a reference to the inherited class or the implemented interface if compatible or null if not compatible:

BaseType b = o as BaseType; // Null if d does not inherit from BaseType.

IInterface i = o as IInterface; // Null if d does not implement IInterface.

If you have only the type T, then use @nikeee's answer.

Answer 2

If you want to check during compilation: Error if if T does NOT implement the desired interface/class, you can use the following constraint

public void MyRestrictedMethod<T>() where T : MyInterface1, MyInterface2, MySuperClass
{
    //Code of my method here, clean without any check for type constraints.
}

I hope that helps.

Answer 3

The correct syntax is

typeof(Employee).IsAssignableFrom(typeof(T))

Documentation

Return Value: true if c and the current Type represent the same type, or if the current Type is in the inheritance hierarchy of c, or if the current Type is an interface that c implements, or if c is a generic type parameter and the current Type represents one of the constraints of c, or if c represents a value type and the current Type represents Nullable<c> (Nullable(Of c) in Visual Basic). false if none of these conditions are true, or if c is null.

source

Explanation

If Employee IsAssignableFrom T then T inherits from Employee.

The usage

typeof(T).IsAssignableFrom(typeof(Employee)) 

returns true only when either

1. T and Employee represent the same type; or,
2. Employee inherits from T.

This may be intended usage in some case, but for the original question (and the more common usage), to determine when T inherits or implements some class/interface, use:

typeof(Employee).IsAssignableFrom(typeof(T))

Answer 4

I believe syntax is: typeof(Employee).IsAssignableFrom(typeof(T));

Answer 5

Although IsAssignableFrom is the best way as others have stated, if you only need to check if a class inherits from another, typeof(T).BaseType == typeof(SomeClass) does the job too.

Answer 6

You can use constraints on the class.

MyClass<T> where T : Employee

Take a look at http://msdn.microsoft.com/en-us/library/d5x73970.aspx