Type variable at function

Question

Good day! This question seems easy, but I can't think out how to do it. I would pass Type parameter to function and check whether variable has that type.

void foo(Type type = ) // how to pass here default value for example System.Object?
{       
        if (elem.GetType() is type) 
        {

        }
    }
}

EDIT I have next classes

class Element {}
class ChildElementClass : Element {}
class SecondChildEleementClass : Element{}

And have array of Elements[], which is storing elements of all three classes

Element[] elements;

So, I would retrieve all elements for ChildElementClass. I make it by other way, but it is just interesting.

https://stackoverflow.com/questions/8708632/passing-objects-by-reference-or-value-in-c-sharp — Emanuel Pirovano, Nov 02 '17 at 11:46
Actually, this question seems like an [XYPropblem](http://meta.stackexchange.com/questions/66377/what-is-the-xy-problem) to me. What is the underling problem that you try to solve? — Zohar Peled, Nov 02 '17 at 11:49
Make the default `null` and check within the function to replace it with your actual default. — Manfred Radlwimmer, Nov 02 '17 at 11:49
What re you trying to achieve ? Why do you need to have a default type ? I can't think of a time where this would make sense ... could be an XY problem — Mathieu VIALES, Nov 02 '17 at 11:50
@NikitaDayneko Why only this one? You can't do it with `object obj = new object()`, `DataTable table = new DataTable()`, etc. You can't initialize non compile-time constant parameters. — SᴇM, Nov 02 '17 at 11:59

PinBack · Accepted Answer · 2017-11-02T11:56:19.117

5

Use this:

void foo(Type type = null)
{
    if (type == null)
        type = typeof(object);
}

See: here

edited Nov 02 '17 at 11:56

answered Nov 02 '17 at 11:50

PinBack

2,499
12
16

jasttim · Answer 2 · 2017-11-02T12:06:20.093

2

you could create a helper method to pass a default value

public void foo(){
   foo(typeof(object));
}
private void foo(Type type){
   //
}

or, set the default type as null and specify a default inside the method

if (type == null) {
    type = typeof(object);
}

edited Nov 02 '17 at 12:06

answered Nov 02 '17 at 11:51

jasttim

723
8
19

How does your answer address OP's problem? – mrogal.ski Nov 02 '17 at 11:54
Good point, I'll adjust this so that it requires less thought – jasttim Nov 02 '17 at 11:58

Type variable at function

2 Answers2