Home

Windows Control: The Button

 

Description

On a typical application, a button is an object that the user clicks to perform an action. To make this obvious, a button is a control surrounded by thick borders. Here is an example of a button on a form:

Button

Although a control is usually positioned on a form, there various other control containers that can hold a button. These include the toolbar or the status bar, and the other containers we have used so far.

To indicate what it is used for, a button displays some text as its caption. A button can also display a picture instead. Another button can display both a string and a picture. When you create a button, you will decide what it should display and how it should behave.

Practical Learning Practical Learning: Introducing Buttons

  1. Start Microsoft Visual C# and create a Windows Application named Algebra2
  2. On the main menu, click Project -> Add Class...
  3. In the Templates list, make sure Class is selected.
    Change the Name to Algebra and click Add
  4. Change the file as follows:
     
    using System;
    
    namespace Algebra2
    {
        public class Algebra
        {
            public static long Factorial(long x)
            {
                if (x <= 1)
                    return 1;
                else
                    return x * Factorial(x - 1);
            }
    
            public static long Permutation(long n, long r)
            {
                if (r == 0)
                    return 0;
                if (n == 0)
                    return 0;
                if ((r >= 0) && (r <= n))
                    return Factorial(n) / Factorial(n - r);
                else
                    return 0;
            }
    
            public static long Combinatorial(long a, long b)
            {
                if (a <= 1)
                    return 1;
    
                return Factorial(a) / (Factorial(b) * Factorial(a - b));
            }
        }
    }
  5. In the Solution Explorer, right-click Form1.cs and click Rename
  6. Type Exercise.cs and press Enter twice (to save and to open the form)
  7. Click the body of the form to make sure it is selected.
    In the Properties window, change the following characteristics
    FormBorderStyle: FixedDialog
    Text: Factorial, Permutation, and Combination
    Size: 304, 208
    StartPosition: CenterScreen
    MaximizeBox: False
    MinimizeBox: False
  8. In the Containers section of the Toolbox, click TabControl and click the form
  9. On the form, right-click the right side of tabPage2 and click Add Page
  10. Based on what we learned in Lesson 24, design the form as follows:
     
    Control Text Name Additional Properties
    TabControl   tclAlgebra HotTrack: True
    Location: 12, 12
    Size: 304, 235
    TabPage Factorial tabFactorial  
    Label Number:   Location: 22, 21
    TextBox   txtNumber TextAlign: Right
    Location: 88, 18
    Size: 50, 20
    Label Result:   Location: 22, 56
    TextBox   txtFactorial TextAlign: Right
    Location: 88, 54
    Size: 140, 20
    Control Text Name Location Size
    TabPage Permutation tabPermutation    
    Label n:   22, 21  
    TextBox   txtPermutationN 88, 18 50, 20
    Label r:   22, 56  
    TextBox   txtPermutationR 88, 54 50, 20
    Label P(n, r):   22, 92  
    TextBox   txtPermutation 88, 90 140, 20
    Control Text Name Location Size
    TabPage Combination tabCombination    
    Label n:   22, 21  
    TextBox   txtCombinationN 88, 18 50, 20
    Label r:   22, 56  
    TextBox   txtCombinationR 88, 54 50, 20
    Label C(n, r):   22, 92  
    TextBox   txtCombination 88, 90 140, 20
  11. Save the form

Creating a Button

To support the buttons of an application, the .NET Framework provides an abstract class named ButtonBase. The regular button of Microsoft Windows is implemented by the Button class. At design time, to add a button to your project, from the Common Controls section of the Toolbox, you can click the Button and click the form or another container.

To programmatically create a button, you can declare a variable of type Button and use the new operator to allocate memory for it. Here is an example:

using System;
using System.Drawing;
using System.Windows.Forms;

public class Exercise : System.Windows.Forms.Form
{
    Button btnResume;

    public Exercise()
    {
        InitializeComponent();
    }

    private void InitializeComponent()
    {
        btnResume = new Button();
        btnResume.Location = new Point(32, 20);

        this.Controls.Add(btnResume);
    }
}

public class Program
{
    static int Main()
    {
        System.Windows.Forms.Application.Run(new Exercise());
        return 0;
    }
}

Practical Learning Practical Learning: Creating Buttons

  1. In the combo box on top of the Properties window, select tabFactorial
  2. From the Common Controls section of the Toolbox, click Button and click on the right side of the top text box
 

Home Copyright © 2007-2012 FunctionX Next