Type Casting TextBox

Question

1.00/5 (1 vote)

See more:

Hi all ,

I have dout abt casting in C# let me explain .

I have third party class which return a System.Window.Form.Textbox.

I want to assign this TextBox to My custom textbox Class .

Below is the Eg of my Custom Class

C#

public class TestTextbox : TextBox
 {
     public override Font Font { get { return base.Font; } set { base.Font = value; } }

 }

but i m not able to cast this

C#

TestTextbox txt = (TestTextbox)(Some method Which returns System.Window.Form.Textbox );

What im missing ,

Thanks in Advance.

Posted 30-Jan-12 20:21pm

Member 4704068

Updated 30-Jan-12 20:23pm

AditSheth

v2

Add a Solution

Comments

Sergey Alexandrovich Kryukov 31-Jan-12 2:51am

You are missing... OOP. The answer by Abhinav is correct; I suggest you accept it formally (green button). Is something is not clear, comment his answer.
--SA

2 solutions

Solution 1

Hi,

Please try,

C#

TestTextbox txt =(method Which returns System.Window.Form.Textbox) as  TestTextbox;

Hope this helps.

Posted 30-Jan-12 20:28pm

manognya kota

Comments

Sergey Alexandrovich Kryukov 31-Jan-12 2:50am

Totally wrong. Please see the answer by Abhinav for the explanation.
Also, you should not give answer which you did not validate. You could check it up with a compiler in no time, but you preferred to just give an answer which turns out to be a plain simple lie. Please don't do such thing. You got a vote of 1, sorry.
--SA

manognya kota 31-Jan-12 2:53am

Yup..checked the question again..how did i miss the basic.. :(

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Abhinav S · Accepted Answer · 2012-01-30T20:29:00

Solution 2

You are deriving from TextBox. As a result, you cannot force a cast of a parent into a child class.
This code simply won't work.

You cannot downcast. TestTextBox will have some additional methods which TextBox may not have.
As a result, if you were able to downcast, those methods would not be available.

Posted 30-Jan-12 20:29pm

Abhinav S

v2

Comments

Sergey Alexandrovich Kryukov 31-Jan-12 2:48am

Abhinav, you should be more precise: this relationship between classes is called "generalization" or "base class (ancestor) -- derived class", not parent/child. Your explanation is correct, I'll case a vote of 4. :-)
--SA

Abhinav S 31-Jan-12 3:20am

Yes I am aware of generalization SA. :)
Thanks though.

manognya kota 31-Jan-12 2:55am

Correct..How did i miss my basic?was more bothered at the syntax :(. my +5