C# Polymorphic object comparison

[Benny_Lava]

Hi, Let's say there are 3 objects: Class A Class B : A Class C : B I want to pass through all objects that derive from Type B C obj1 = new C(); B obj2 = new B(); if(obj1.GetType() == typeof(B)) { //--Pass through all objects that derive from object B or object A... } typeof comapares directly the top types C must equal C... No polymorphic comarison... How to do a polymorphic comparison? Which keyword or mechanism to use? Thanks!

[Lukasz Nowakowski]

if(obj1 is B) should work for you

[OriginalGriff]

As lukasz_nowakowski says, is is what you want. The alternative is as

if (obj is B)
{
B bInstance = (B) obj;
...
}

or

B bInstance = obj as B;
if (bInstance != null)
{
...
}

You can use either, I prefer the second as I prefer explicit null tests. That's just personal preference though.

Did you know: That by counting the rings on a tree trunk, you can tell how many other trees it has slept with.

[Lukasz Nowakowski]

If you want to just add it to objects' list, then is is enough, but if you want to use object obj as instance of class B, then B instance = obj as B; is the path to follow. To find out why read for example this[^].

[Benny_Lava]

Thank you!!

[Benny_Lava]

The work with polymorphic objects after comparison is very clear to me. I just didn't know how to compare them in C#... Thanks!

[LookSharp]

FYI - while the use of is and as are what's appropriate for your problem, as lukasz_nowakowski and OriginalGriff have said, your example code used GetType ... which put me in mind of how to do a similar test on Types, rather than objects:

Type typeOfC = typeof(C);
Type typeofSomeObject = someObject.GetType();

// ...
if (typeOfC.IsAssignableFrom(typeofSomeObject))
	{
	// ...
	}
// ...