How to know the based class of a class using code at runtime not Object Browser at design time?

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I wonder if we can know the based class of some class using some code (programmatically), of course, we can know that at design time by using Object Browser, but at runtime, can we know that? For example, I have a custom textbox named "QTextBox" derived from the .NET class "TextBox", but anyone else may not know that, and how can they do to check that? I think it is important to know that before any further handlings with the objects of QTextBox concerning polymorphism, type casting...
I ask this question but I think we may not have any ways!
Thank you so much!

Posted 8-May-11 19:56pm

King Boy

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Sergey Alexandrovich Kryukov · Accepted Answer · 2011-05-08T20:09:00

Solution 1

Reflection. for a variable v, call v.GetType(), or for a type T, call typeof(T). Both expression will return an object of the type System.Type. Check the instance property System.Type.BaseType. Repeat until recursively until you learn all the inheritance chain to the very base type, which is always System.Object.

—SA

Posted 8-May-11 20:09pm

Sergey Alexandrovich Kryukov

Comments

Hemant__Sharma 9-May-11 2:11am

ohh. i was few seconds late.. :)

Sergey Alexandrovich Kryukov 9-May-11 10:14am

:-)

[no name] 9-May-11 7:29am

Wow! That's exactly what I want! Thank you so much!

Sergey Alexandrovich Kryukov 9-May-11 10:14am

I knew that... :-)
OK, thanks for accepting this answer.
Good luck, call again,
--SA

OriginalGriff · Accepted Answer · 2011-05-08T20:11:00

Solution 3

There is a tip here: Following object inheritance[^] which does just that - it follows the inheritance chain all the way back.

Posted 8-May-11 20:11pm

OriginalGriff

Comments

Sergey Alexandrovich Kryukov 9-May-11 3:10am

Yes, my 5, but I described the pseudo-code in a couple of lines.
Please see.
--SA

Sander Rossel · Accepted Answer · 2011-05-08T20:22:00

Good answer by SAKryukov. Want to add some to it.
If you simply want to check if an Object is a derived of another you can do the following:

C#

QTextBox qtb = new QTextBox();
TextBox tb = qtb as TextBox; // Called TryCast in VB. It tries to cast one Object to another.
if (tb == null)
{
   // Conversion failed, QTextBox is not a derived of TextBox.
}
else
{
   // Conversion succeeded, QTextBox is a derived of TextBox.
}

Edit:
I have used the "as" operator[^]. The "as" operator is equal to TryCast in VB, which describes it pretty well I think. Follow the link for an example and short description "The as operator is used to perform certain types of conversions between compatible reference types. The as operator is like a cast operation. However, if the conversion is not possible, as returns null instead of raising an exception.".

Hemant__Sharma · Accepted Answer · 2011-05-08T20:10:00

Solution 2

yes you can:

C#

public class A
    {
        public string StringA;
        public A()
        {
            StringA = "StringA";
        }
    }

    public class B : A
    {
        public string StringB;
        public B()
        {
            StringA = "StringA";
            StringB = "StringB";
        }
    }
    class Program
    {

        static void Main(string[] args)
        {
            B bObject = new B();
            Type baseType = bObject.GetType().BaseType;
            string baseClassName = baseType.Name;
        }

    }

Posted 8-May-11 20:10pm

Hemant__Sharma

Comments

Sergey Alexandrovich Kryukov 9-May-11 3:09am

Not so good.
Working with names is a dirty way. You can get type of the type Type and compare them, the type Type has semantic equivalence operator. If TypeA == TypeB...
--SA

Hemant__Sharma 9-May-11 5:12am

Well I just used an example on How to get "base type". I didn't use the baseClassName further and I believe @King Boy is smart enough to understand what to do once he has .GetType().BaseType otherwise the intellisense will tell me what to do next.
Thanks,
Hemant