Added DependsOn attributes.

src/Perspex.Controls/Primitives/SelectingItemsControl.cs

@@ -11,6 +11,7 @@ using Perspex.Controls.Generators;
 using Perspex.Data;
 using Perspex.Input;
 using Perspex.Interactivity;
+using Perspex.Metadata;
 using Perspex.Styling;
 using Perspex.VisualTree;
 
@@ -125,6 +126,7 @@ namespace Perspex.Controls.Primitives
         /// <summary>
         /// Gets or sets the index of the selected item.
         /// </summary>
+        [DependsOn(nameof(Items))]
         public int SelectedIndex
         {
             get
@@ -149,6 +151,7 @@ namespace Perspex.Controls.Primitives
         /// <summary>
         /// Gets or sets the selected item.
         /// </summary>
+        [DependsOn(nameof(Items))]
         public object SelectedItem
         {
             get

src/Perspex.Styling/Styling/Setter.cs

@@ -50,6 +50,7 @@ namespace Perspex.Styling
         /// </summary>
         [Content]
         [AssignBinding]
+        [DependsOn(nameof(Property))]
         public object Value
         {
             get;