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

There is a Method called Type.IsAssignableFrom().

To check if T inherits/implements Employee:

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

If you are targeting .NET Core, the method has moved to TypeInfo:

typeof(Employee).GetTypeInfo().IsAssignableFrom(typeof(T).Ge‌​tTypeInfo())

Answer 2

What everyone really means is:

typeof(BaseType).IsAssignableFrom(typeof(DerivedType)) // => true

because you can literally assign from an instance of a DerivedType to an instance of a BaseType:

DerivedType childInstance = new DerivedType();
BaseType parentInstance = childInstance; // okay, assigning base from derived
childInstance = (DerivedType) parentInstance; // not okay, assigning derived from base

when

public class BaseType {}
public class DerivedType : BaseType {}

---

And some concrete examples if you're having trouble wrapping your head around it:

(via LinqPad, hence the HorizontalRun and Dump)

void Main()
{
    // http://stackoverflow.com/questions/10718364/check-if-t-inherits-or-implements-a-class-interface

    var b1 = new BaseClass1();

    var c1 = new ChildClass1();
    var c2 = new ChildClass2();
    var nb = new nobase();

    Util.HorizontalRun(
        "baseclass->baseclass,child1->baseclass,baseclass->child1,child2->baseclass,baseclass->child2,nobase->baseclass,baseclass->nobase",
        b1.IsAssignableFrom(typeof(BaseClass1)),
        c1.IsAssignableFrom(typeof(BaseClass1)),
        b1.IsAssignableFrom(typeof(ChildClass1)),
        c2.IsAssignableFrom(typeof(BaseClass1)),
        b1.IsAssignableFrom(typeof(ChildClass2)),
        nb.IsAssignableFrom(typeof(BaseClass1)),
        b1.IsAssignableFrom(typeof(nobase))
        ).Dump("Results");

    var results = new List<string>();
    string test;

    test = "c1 = b1";
    try {
        c1 = (ChildClass1) b1;
        results.Add(test);
    } catch { results.Add("FAIL: " + test); }

    test = "b1 = c1";
    try {
        b1 = c1;
        results.Add(test);
    } catch { results.Add("FAIL: " + test); }

    test = "c2 = b1";
    try {
        c2 = (ChildClass2) b1;
        results.Add(test);
    } catch { results.Add("FAIL: " + test); }

    test = "b1 = c2";
    try {
        b1 = c2;
        results.Add(test);
    } catch { results.Add("FAIL: " + test); }

    results.Dump();
}

// Define other methods and classes here
public static class exts {
    public static bool IsAssignableFrom<T>(this T entity, Type baseType) {
        return typeof(T).IsAssignableFrom(baseType);
    }
}


class BaseClass1 {
    public int id;
}

class ChildClass1 : BaseClass1 {
    public string name;
}

class ChildClass2 : ChildClass1 {
    public string descr;
}

class nobase {
    public int id;
    public string name;
    public string descr;
}

Results

baseclass->baseclass

True

child1->baseclass

False

baseclass->child1

True

child2->baseclass

False

baseclass->child2

True

nobase->baseclass

False

baseclass->nobase

False

and

• FAIL: c1 = b1
• b1 = c1
• FAIL: c2 = b1
• b1 = c2