MessageBox.md

MessageBox

A modal dialog for simple confirmations and notifications. Supports multiple button configurations, danger styling, additional text (e.g. stack traces), and arbitrary extra content with value capture.

Basic usage

string result = await MessageBox.Show(window, "Confirm", "Do you want to proceed?");
// result == "OK"

Button configurations

// OK / Cancel
string result = await MessageBox.Show(window, "Confirm", "Save changes?",
    new[]
    {
        new MessageBoxButton { Text = "OK",     Result = "OK",     Default = true, IsKeyDown = true },
        new MessageBoxButton { Text = "Cancel", Result = "Cancel" }
    });

// Yes / No / Cancel
string result = await MessageBox.Show(window, "Question", "Save before closing?",
    new[]
    {
        new MessageBoxButton { Text = "Yes",    Result = "Yes",    Default = true, IsKeyDown = true },
        new MessageBoxButton { Text = "No",     Result = "No" },
        new MessageBoxButton { Text = "Cancel", Result = "Cancel" }
    });

MessageBoxButton properties

Property	Type	Description
Text	string	Button label
Result	string	Value returned when clicked
Default	bool	Gets accent/danger styling and is the Enter-key target
IsKeyDown	bool	Enter key triggers this button
ThemeKey	string?	Resource key of a ControlTheme to apply (e.g. "DangerButtonTheme")

Danger style

string result = await MessageBox.Show(window,
    "Delete account",
    "This action is irreversible.",
    new[]
    {
        new MessageBoxButton { Text = "Delete", Result = "Delete", Default = true },
        new MessageBoxButton { Text = "Cancel", Result = "Cancel", IsKeyDown = true }
    },
    style: MessageBoxStyle.Danger);

The danger style shows a red header with a warning icon. The default button automatically gets DangerButtonTheme.

With additional text (stack trace / details)

await MessageBox.Show(window, "Error", "An unexpected error occurred.",
    new[] { new MessageBoxButton { Text = "OK", Result = "OK", Default = true } },
    additionalText: exception.ToString());

The additional text is rendered in a read-only monospace TextBox with horizontal scroll.

Custom extra content with value capture

var radio1 = new RadioButton { Content = "Keep existing", GroupName = "g", IsChecked = true };
var radio2 = new RadioButton { Content = "Replace",       GroupName = "g" };
var panel  = new StackPanel  { Children = { radio1, radio2 } };

var result = await MessageBox.Show<string>(window,
    "Conflict",
    "A file with this name already exists.",
    extraContent: panel,
    valueSelector: _ => radio1.IsChecked == true ? "keep" : "replace",
    buttons: new[]
    {
        new MessageBoxButton { Text = "OK",     Result = "OK",     Default = true },
        new MessageBoxButton { Text = "Cancel", Result = "Cancel" }
    });

// result.Button == "OK" or "Cancel"
// result.Value == "keep" or "replace"

onContentReady callback

Wire up event handlers on the extra content before the dialog is shown:

var check = new CheckBox { Content = "Don't show again" };

await MessageBox.Show(window, "Info", "Welcome!",
    extraContent: check,
    onContentReady: ctrl =>
    {
        ((CheckBox)ctrl).IsCheckedChanged += (_, _) => UpdatePreference();
    });