A Windows Phone 7 App from the Ground Up

using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using Microsoft.Phone.Controls;

namespace MyLastFm
{
    static class StateDictionaryExtenstions
    {
        public static void PreserveState(this IDictionary<string, object> state, Pivot pivot)
        {
            state[pivot.Name + "_SelectedIndex"] = pivot.SelectedIndex;
        }
        public static void RestoreState(this IDictionary<string, object> state, Pivot pivot)
        {
            int index = TryGetValue<int>(state, pivot.Name + "_SelectedIndex", -1);
            if (pivot.Items.Count >= index)
            {
                pivot.Dispatcher.BeginInvoke(() => pivot.SelectedIndex = index);                
            }
        }

        public static void PreserveState(this IDictionary<string, object> state, TextBox textBox)
        {
            state[textBox.Name + "_Text"] = textBox.Text;
            state[textBox.Name + "_SelectionStart"] = textBox.SelectionStart;
            state[textBox.Name + "_SelectionLength"] = textBox.SelectionLength;
        }
        public static void RestoreStatethis(IDictionary<string, object> state, TextBox textBox, string defaultValue)
        {
            textBox.Text = TryGetValue<string>(state, textBox.Name + "_Text", defaultValue);
            textBox.SelectionStart = TryGetValue<int>(state, textBox.Name + "_SelectionStart", textBox.Text.Length);
            textBox.SelectionLength = TryGetValue<int>(state, textBox.Name + "_SelectionLength", 0);
        }

        public static void PreserveState(this IDictionary<string, object> state, ScrollViewer scrollViewer)
        {
            state[scrollViewer.Name + "_VerticalOffset"] = scrollViewer.VerticalOffset;
        }
        public static void RestoreState(this IDictionary<string, object> state, ScrollViewer scrollViewer)
        {
            double offset = TryGetValue<double>(state, scrollViewer.Name + "_VerticalOffset", 0);
            if (offset > 0)
            {
                scrollViewer.Dispatcher.BeginInvoke(() => scrollViewer.ScrollToVerticalOffset(offset));
            }
        }

        public static void PreserveState(this IDictionary<string, object> state, WebBrowser webBrowser)
        {
            state[webBrowser.Name + "_Content"] = webBrowser.SaveToString();
        }
        public static void RestoreState(IDictionary<string, object> state, WebBrowser webBrowser)
        {
            string content = TryGetValue<string>(state, webBrowser.Name + "_Content", "");
            if (!string.IsNullOrEmpty(content))
            {
                webBrowser.Loaded += new RoutedEventHandler(delegate(object sender, RoutedEventArgs e2)
                {
                    webBrowser.NavigateToString(content);
                });
            }
        }

        public static void PreserveFocusState(this IDictionary<string, object> state, FrameworkElement parent)
        {
            // Determine which control currently has focus.
            Control focusedControl = FocusManager.GetFocusedElement() as Control;

            // If no control has focus, store null in the State dictionary.
            if (focusedControl == null)
            {
                state["FocusedControlName"] = null;
            }
            else
            {
                // Find the control within the parent
                Control foundFE = parent.FindName(focusedControl.Name) as Control;

                // If the control isn't found within the parent, store null in the State dictionary.
                if (foundFE == null)
                {
                    state["FocusedElementName"] = null;
                }
                else
                {
                    // otherwise store the name of the control with focus.
                    state["FocusedElementName"] = focusedControl.Name;
                }
            }
        }
        public static void RestoreFocusState(this IDictionary<string, object> state, FrameworkElement parent)
        {
            // Get the name of the control that should have focus.
            string focusedName = TryGetValue<string>(state, "FocusedElementName", null);

            // Check to see if the name is null or empty
            if (!String.IsNullOrEmpty(focusedName))
            {

                // Find the control name in the parent.
                Control focusedControl = parent.FindName(focusedName) as Control;
                if (focusedControl != null)
                {
                    // If the control is found, call its Focus method.
                    parent.Dispatcher.BeginInvoke(() => { focusedControl.Focus(); });
                }
            }
        }

        public static T TryGetValue<T>(this IDictionary<string, object> state, string name, T defaultValue)
        {
            if (state.ContainsKey(name))
            {
                if (state[name] != null)
                {
                    return (T)state[name];
                }
            }
            return defaultValue;
        }
    }
}