Question

I’m having some issues getting silverlight 4 to set initial focus on a control, the biggest issue is that if the control has not rendered focus is not guaranteed.

Answer 1

I have created a behavior and it sets the focus in the Loaded event which guarantees the control is loaded.

using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Input;
using System.Windows.Interactivity;

namespace xxx.Behaviors
{
    public class SetControlFocusBehavior : Behavior<Control>
    {
        protected override void OnAttached()
        {
            base.OnAttached();

            if (AssociatedObject is Control)
            {
                ((Control)AssociatedObject).Loaded += new RoutedEventHandler(SetControlFocusBehavior_Loaded);
            }
        }

        void SetControlFocusBehavior_Loaded(object sender, RoutedEventArgs e)
        {
            var control = sender as Control;

            if (control == null)
            {
                return;
            }

            System.Windows.Browser.HtmlPage.Plugin.Focus();
            control.Focus();
        }

        protected override void OnDetaching()
        {
            base.OnDetaching();
            ((Button)AssociatedObject).Loaded -= SetControlFocusBehavior_Loaded;
        }
    }
}

To use it, simply drag and drop it onto the control using Blend.

            <TextBox x:Name="MyTextBox">
                <i:Interaction.Behaviors>
                    <sg:SetControlFocusBehavior/>
                </i:Interaction.Behaviors>
            </TextBox>