how to display textBox control in MessageBox?

You can't. MessageBox is a special container designed to only show a message and buttons. Instead, you can create your own Form with whatever controls you want, and use .ShowDialog() on it.

You can simply add an Input box from VB.NET into your C# project. First add Microsoft.VisualBasic to your project References, then use the following code:

string UserAnswer = Microsoft.VisualBasic.Interaction.InputBox("Your Message ", "Title", "Default Response");

And that should work properly.

It will be better to add a new Form in you application which you can customize the way you want.

and just call it from where ever required.