Event Bindings Examples

In this examples we will introduce the XAML example followed by the equivalent code in C#. The code is written for WPF platforms but it should be the same for the remaining platforms. Please remember:

• UI elements names start with $ or !.
• UI resources keys start with # or !.
• Keywords start with @ or !.
• The symbol ! will search for keyword, then UI element, then UI resource.
• Multiple events definitions are separated by ,.

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1. Simple default event binding to a method that has no parameters:

<Button tools.Events.Bindings="Cancel"/>

Or:

<Button tools.Events.Bindings="Cancel()"/>

Private void Button_Click(object sender, EventArgs e)
{
    (Button.DataContext as ViewModel).Cancel();
}

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2. Binding an event to a method that takes single parameter and pass the Text property of the control to the method:

<TextBox tools.Events.Bindings="LostFocus=ValidateName(!this.Text)"/>

Or:

<TextBox tools.Events.Bindings="LostFocus=ValidateName(@this.Text)"/>

Private void TextBox_LostFocus(object sender, EventArgs e)
{
    var textBox = sender as TextBox;
    (textBox.DataContext as ViewModel).ValidateName(textBox.Text);
}

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3. Binding to method in a data context in another control:

<TextBox tools.Events.Bindings="LostFocus=$root.DataContext.ValidateName(!this.Text),GotFocus=!root.Clear(@sender)"/>

Starting by v1.2.0 you can delete DataContext part of the path and just write:

<TextBox tools.Events.Bindings="LostFocus=$root.ValidateName(!this.Text),GotFocus=!root.DataContext.Clear(@sender)"/>

Both syntax can be translated to the following C# code:

Private void TextBox_LostFocus(object sender, EventArgs e)
{
    var textBox = sender as TextBox;
    var root = textBox.GetName("root");
    (root.DataContext as ViewModel).ValidateName(textBox.Text);
}
Private void TextBox_GotFocus(object sender, EventArgs e)
{
    var textBox = sender as TextBox;
    var root = textBox.GetName("root");
    (root.DataContext as ViewModel).Clear(sender);
}

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4. Binding an event to a command and pass the Text property of the control to the `Execute' method:

<TextBox tools.Events.Bindings="LostFocus=ValidateNameCommand(!this.Text)"/>

Or:

<TextBox tools.Events.Bindings="LostFocus=ValidateNameCommand(@this.Text)"/>

Private void TextBox_LostFocus(object sender, EventArgs e)
{
    var textBox = sender as TextBox;
    var command = (textBox.DataContext as ViewModel).ValidateNameCommand as ICommand;
    if (command.CanExecute(textBox.Text)) command.Execute(textBox.Text);
}

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