Making an input box similar to Visual Basic input box

Question

I have made an InputBox class that returns a string but I want the class to return a string upon exit.

I want it to behave exactly like the Visual Basic Input Box.

For now I have passed a mutable string value into the constructor and change it that way. But then I realized the Visual Basic input box is way better.

myValue = InputBox(message, title, defaultValue)

How can I create my own InputBox class like this? I realize I can import the VB inputbox to c# but I want to make my own custom InputBox.

Edit: I guess the reason I am so fascinated by this is because Visual Basic lets you call a function without putting the name of the class. I wish there was a way of doing this in C# without using delegates. I think my solution may be to create a function which encapsulates my form. So perhaps I will rephrase my question to is there a way I can return a value through something that behaves visually like a class?

I think the only time you can call a static function in C# without specifying what class it is from is if the function was declared in the class you are currently writing code for. If it was a constructor you would need new. So I don't think you can have it be the same syntax as in VB, but that shouldn't matter - C# is not VB, it doesn't need to have the same syntax. — Patashu
– Patashu, Commented Jun 13, 2013 at 1:09
Winforms but Simon has given me the Holy Grail, the ultimate tool to make all my classes look like functions! I will just use implicit operator to make classes look like functions but they will be very modular functions. — CodeCamper
– CodeCamper, Commented Jun 13, 2013 at 1:31

Simon Whitehead · Accepted Answer · 2013-06-13 01:09:23Z

1

You are incorrect in assuming that the Visual Basic InputBox is a class. It is, in fact, a function. Here is the method definition:

Public Function InputBox( _
    ByVal Prompt As String, _
    Optional ByVal Title As String = "", _
    Optional ByVal DefaultResponse As String = "", _
    Optional ByVal Xpos As Integer = -1, _
    Optional ByVal YPos As Integer = -1 _
) As String

Digging a little deeper, it resides in Microsoft.VisualBasic.dll as a method of the Interaction class.

The closest way to simulate the VB.NET syntactic sugar is to implicitly convert your custom InputBox to a string, e.g:

public class InputBox
{
    private string _title;

    public InputBox(string title)
    {
        _title = title;
    }

    public static implicit operator string(InputBox from)
    {
        return from._title;
    }
}

// .. elsewhere ..
 string title = new InputBox("Test");
 Console.WriteLine(title); // prints Test

.. although I'm not sure if I'd do this personally.

Obviously title is an example. Your InputBox class would spawn a Form (or inherit from it) and return the input into the form.

..may I ask why you're looking to replicate this?

answered Jun 13, 2013 at 1:09

Simon Whitehead

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8 Comments

CodeCamper Over a year ago

I miss the ability to have simple functions that I will reuse in all my programs. Such as the old MsgBox and InputBox where it is so common to ask a user for input in a standardized dialogue box. It seems silly to have to use the name of the class or create a delegate just so I don't have to type it out. I am making my own dialogue boxes for a game I am making. I am fascinated by this implicit operator string I have never seen this before and think I will definitely use it! Can you go into more detail of how exactly this works? So I can create an implicit operator for every data type???

CodeCamper Over a year ago

Wow I thank you so much for this implicit operator code which I have never seen before. Now I have a whole bunch of ideas to feed my functional based programming desires! You just gave me the tool I need to turn C# into a more functional programming language against everyone else' will!

Simon Whitehead Over a year ago

I think my example is as close as you'll get. You're looking for something similar to the friend keyword in C++.. which doesn't exist in C# in the same way. The above example is purely operator overloading.. in this case, its the implicit operator from InputBox to string. Operator overloading isn't extremely common in C# (from what I've seen), but it should definitely be at least understood by a C# developer.

CodeCamper Over a year ago

Your example is great! I will definitely research more into the friend keyword and the differences. friend sounds like my friend. Now I will begin to make almost all my classes into wannabe functions. I never thought about how integer and double knew to implicitly convert and this answers that question. I guess it is uncommon because it really lets you turn C# into a more functional looking language which C# is trying to turn people away from. Don't you miss in VB6 just being able to write MsgBox? I am so making my own MsgBox class that behaves like a function with all modular behavior.

Simon Whitehead Over a year ago

I would warn you about the perils of operator overloading.. but I think it's best if you learn it for yourself :) Glad I could help anyway.

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