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How to open a message box (WPF .NET)

  • Artikel

A message box is a dialog box that is used to quickly display information and optionally allow users to make decisions. Access to the message box is provided by the MessageBox class. A message box is displayed modally. And the code that displays the message box is paused until the user closes the message box either with the close button or a response button.

The following illustration demonstrates the parts of a message box:

A figure that shows the parts of a message box for WPF.

  • A title bar with a caption (1).
  • A close button (2).
  • Icon (3).
  • Message displayed to the user (4).
  • Response buttons (5).

For presenting or gathering complex data, a dialog box might be more suitable than a message box. For more information, see Dialog boxes overview.

Display a message box

To create a message box, you use the MessageBox class. The MessageBox.Show method lets you configure the message box text, title, icon, and buttons, shown in the following code:

string messageBoxText = "Do you want to save changes?";
string caption = "Word Processor";
MessageBoxButton button = MessageBoxButton.YesNoCancel;
MessageBoxImage icon = MessageBoxImage.Warning;
MessageBoxResult result;

result = MessageBox.Show(messageBoxText, caption, button, icon, MessageBoxResult.Yes);

Dim messageBoxText As String = "Do you want to save changes?"
Dim caption As String = "Word Processor"
Dim Button As MessageBoxButton = MessageBoxButton.YesNoCancel
Dim Icon As MessageBoxImage = MessageBoxImage.Warning
Dim result As MessageBoxResult

result = MessageBox.Show(messageBoxText, caption, Button, Icon, MessageBoxResult.Yes)

The MessageBox.Show method overloads provide ways to configure the message box. These options include:

  • Title bar caption
  • Message icon
  • Message text
  • Response buttons

Here are some more examples of using a message box.

  • Display an alert.

    MessageBox.Show("Unable to save file, try again.");

    MessageBox.Show("Unable to save file, try again.")

    The previous code displays a message box like the following image:

    A simple message box for WPF that has no options configured.

    It's a good idea to use the options provided by the message box class. Using the same alert as before, set more options to make it more visually appealing:

    MessageBox.Show("Unable to save file, try again.", "Save error", MessageBoxButton.OK, MessageBoxImage.Error);

    MessageBox.Show("Unable to save file, try again.", "Save error", MessageBoxButton.OK, MessageBoxImage.Error)

    The previous code displays a message box like the following image:

    A warning message box for WPF that has an icon, caption, and text.

  • Display a warning.

    MessageBox.Show("If you close the next window without saving, your changes will be lost.", "Configuration", MessageBoxButton.OK, MessageBoxImage.Warning);

    MessageBox.Show("If you close the next window without saving, your changes will be lost.", "Configuration", MessageBoxButton.OK, MessageBoxImage.Warning)

    The previous code displays a message box like the following image:

    A simple message box for WPF that has displays a warning icon.

  • Ask the user a question.

    if (MessageBox.Show("If the file save fails, do you want to automatically try again?",
                    "Save file",
                    MessageBoxButton.YesNo,
                    MessageBoxImage.Question) == MessageBoxResult.Yes)
{
    // Do something here
}

    If MessageBox.Show("If the file save fails, do you want to automatically try again?",
                   "Save file",
                   MessageBoxButton.YesNo,
                   MessageBoxImage.Question) = MessageBoxResult.Yes Then

    ' Do something here

End If

    The previous code displays a message box like the following image:

    A simple message box for WPF that prompts the user with a yes or no question.

Handle a message box response

The MessageBox.Show method displays the message box and returns a result. The result indicates how the user closed the message box:

result = MessageBox.Show(messageBoxText, caption, button, icon, MessageBoxResult.Yes);

switch (result)
{
    case MessageBoxResult.Cancel:
        // User pressed Cancel
        break;
    case MessageBoxResult.Yes:
        // User pressed Yes
        break;
    case MessageBoxResult.No:
        // User pressed No
        break;
}

result = MessageBox.Show(messageBoxText, caption, Button, Icon, MessageBoxResult.Yes)

Select Case result
    Case MessageBoxResult.Cancel
        ' User pressed Cancel
    Case MessageBoxResult.Yes
        ' User pressed Yes
    Case MessageBoxResult.No
        ' User pressed No
End Select

When a user presses the buttons at the bottom of the message box, the corresponding MessageBoxResult is returned. However, if the user presses the ESC key or presses the Close button (#2 in the message box illustration), the result of the message box varies based on the button options:

Button options ESC or Close button result
OK OK
OKCancel Cancel
YesNo ESC keyboard shortcut and Close button disabled. User must press Yes or No.
YesNoCancel Cancel

For more information on using message boxes, see MessageBox and the MessageBox sample.

See also