Add UI enhancements and selection functionality to DropdownWindow

Added Title, dimensions, and startup location to DropdownWindow. Introduced "Show Selected" and "Set Selection" buttons for better UI interaction. Modified Dropdown class to include SetSelectedItem method and improve item selection handling.

Frank.Wpf.Controls.SimpleInputs/Dropdown.cs

@@ -25,6 +25,17 @@ public required Func<T, string> DisplayFunc
     }
 
     public required Action<T> SelectionChangedAction { get; init; }
+
+    public void SetSelectedItem(T item)
+    {
+        // Ensure the item is in the list
+        if (!Items.Contains(item))
+            throw new ArgumentException("Item is not in the list of items");
+
+        _comboBox.SelectedItem = item;
+    }
+
+    public T? SelectedItem => _comboBox.SelectedItem is T item ? item : default;
 
     private void ComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
     {

Frank.Wpf.Tests.App/Windows/DropdownWindow.cs

@@ -7,11 +7,16 @@ namespace Frank.Wpf.Tests.App.Windows;
 public class DropdownWindow : Window
 {
 
-    private readonly Dropdown<MyClass> _dropdown;
+    private readonly Dropdown<MyClass?> _dropdown;
 
     public DropdownWindow()
     {
-        _dropdown = new Dropdown<MyClass>()
+        Title = "Dropdown Window";
+        Width = 400;
+        Height = 300;
+        WindowStartupLocation = WindowStartupLocation.CenterScreen;
+
+        _dropdown = new Dropdown<MyClass?>()
         {
             Items = new List<MyClass>
             {
@@ -22,9 +27,46 @@ public DropdownWindow()
             DisplayFunc = x => x.Name,
             SelectionChangedAction = x => { MessageBox.Show($"Selected {x.Name} with Id {x.Id} and Age {x.Age}"); }
         };
+        var showSelectedButton = new Button()
+        {
+            Content = "Show Selected",
+            Margin = new Thickness(0, 10, 0, 0)
+        };
+        showSelectedButton.Click += (sender, args) =>
+        {
+            var selected = _dropdown.SelectedItem;
+            MessageBox.Show($"Selected {selected.Name} with Id {selected.Id} and Age {selected.Age}");
+        };
+
+        var setSelectionButton = new Button()
+        {
+            Content = "Set Selection",
+            Margin = new Thickness(0, 10, 0, 0)
+        };
+        setSelectionButton.Click += (sender, args) =>
+        {
+            var random = new Random();
+            var randomIndex = random.Next(0, _dropdown.Items.Count());
+            MyClass? randomItem = null;
+            while (randomItem == null)
+            {
+                var item = _dropdown.Items.ElementAt(randomIndex);
+                if (item != _dropdown.SelectedItem)
+                {
+                    randomItem = item;
+                }
+                else
+                {
+                    randomIndex = random.Next(0, _dropdown.Items.Count());
+                }
+            }
+            _dropdown.SetSelectedItem(randomItem);
+        };
 
         var stackPanel = new StackPanel();
         stackPanel.Children.Add(_dropdown);
+        stackPanel.Children.Add(showSelectedButton);
+        stackPanel.Children.Add(setSelectionButton);
 
         Content = stackPanel;
     }