Project Clock

Radio Buttons

There are two groups of radio buttons presented in the window shown in Figure 19-3. If a radio button is chosen in RadioGroup1, the event handler associated with that button is immediately actuated. When this method is chosen , the user has no time to recover from a mistake (picking the wrong radio button).

Figure 19-3: Radio Buttons window

The RadioGroup2 scheme allows the user to pick a button, change her mind and pick a different button, then invoke the proper event handler when the Go! button is clicked.

Since each group of three radio buttons was placed onto a group box, the three buttons act like radio buttons are supposed to: Only one of the group can be selected. If the programmer does not create a group box first (and set each radio button onto that group box), the radio buttons all interact independently, thus defeating the purpose of a list of buttons.

The radio button code is shown below:

Form3

 Form3.cs: SC0500:       #region Using directives               7 lines, same as SC0002  SC0008] SC0508:       #endregion SC0509:       namespace StandardControls SC0510:       { SC0511:         partial class Form3 : Form SC0512:         { SC0513:           public Form3() SC0514:           { SC0515:             InitializeComponent(); SC0516:           } //-----------------------------------------------------------------------------------------// SC0520:           private void radioButton2_CheckedChanged(object sender, EventArgs e) SC0521:           { // radioButton2. SC0522:             MessageBox.Show("radioButton2 picked."); SC0522B:            return; SC0523:             // Close(); SC0524:           } //-----------------------------------------------------------------------------------------// SC0530:           private void radioButton3_CheckedChanged(object sender, EventArgs e) SC0531:           { // radioButton3. SC0532:             MessageBox.Show("radioButton3 picked."); SC0533:             Close(); SC0534:           } //-----------------------------------------------------------------------------------------// SC0540:           private void radioButton4_CheckedChanged(object sender, EventArgs e) SC0541:           { // radioButton4. SC0542:             MessageBox.Show("radioButton4 picked."); SC0543:             Close(); SC0544:           } //-----------------------------------------------------------------------------------------// SC0550:           private void button1_Click(object sender, EventArgs e) SC0551:           { // radioGroup2 Go!. SC0552:             if (radioButton5.Checked)                     MessageBox.Show("radioButton5 picked."); SC0553:             else if (radioButton6.Checked)                     MessageBox.Show("radioButton6 picked."); SC0554:             else if (radioButton7.Checked)                     MessageBox.Show("radioButton7 picked."); SC0555:             Close(); SC0556:           } //-----------------------------------------------------------------------------------------// SC0560:           private void button2_Click(object sender, EventArgs e) SC0561:           { // Quit. SC0562:             Close(); SC0563:           } SC0564:         } SC0565:       } //========================================================================================// Form3.Designer.cs: SC0600:       namespace StandardControls SC0601:       {                 [1 label, 2 groupBoxes, 6 radioButtons, 2 buttons] SC0733:       } 

The return statement in line SC0522B was placed there to demonstrate the difference between return and Close(): return (line SC0522B) returns to Figure 19-3, and Close() (line SC0523) reverts to the main window, which is shown in Figure 19-1 (the window that created Figure 19-3). We seldom exit a control event handler like this with a return unless it is a text-checking handler.

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Unlocking Microsoft C# V 2.0 Programming Secrets (Wordware Applications Library)

ISBN: 1556220979
EAN: 2147483647

Year: 2005
Pages: 129

Authors: Richard Braden

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