Nullable review

src/MahApps.Metro.Samples/MahApps.Metro.Demo/ExampleViews/MultiSelectionComboBoxExample.xaml.cs

@@ -16,18 +16,24 @@ public partial class MultiSelectionComboBoxExample : UserControl
     {
         public MultiSelectionComboBoxExample()
         {
-            InitializeComponent();
+            this.InitializeComponent();
         }
 
-        private void Mscb_Example_AddingItem(object sender, AddingItemEventArgs args)
+        private void Mscb_Example_AddingItem(object? sender, AddingItemEventArgs args)
         {
             // We don't want to get double entries so let`s check if we already have one.
-            args.Accepted = !args.TargetList.Contains(args.ParsedObject);
+            args.Accepted = args.TargetList is not null && !args.TargetList.Contains(args.ParsedObject);
         }
 
-        private async void Mscb_Example_AddedItem(object sender, AddedItemEventArgs args)
+        private async void Mscb_Example_AddedItem(object? sender, AddedItemEventArgs args)
         {
-            await this.TryFindParent<MetroWindow>()?.ShowMessageAsync("Added Item", $"Successfully added \"{args.AddedItem}\" to your Items-Collection");
+            var window = this.TryFindParent<MetroWindow>();
+            if (window is null)
+            {
+                return;
+            }
+
+            await window.ShowMessageAsync("Added Item", $"Successfully added \"{args.AddedItem}\" to your Items-Collection");
         }
 
         private void mscb_Example_SelectionChanged(object sender, SelectionChangedEventArgs e)
@@ -43,4 +49,4 @@ private void mscb_Example_SelectionChanged(object sender, SelectionChangedEventA
             }
         }
     }
-}
+}

src/MahApps.Metro.Samples/MahApps.Metro.Demo/Models/Album.cs

@@ -76,7 +76,7 @@ public virtual Artist? Artist
 
         public override string ToString()
         {
-            return $"{Artist}: {Title} ({Price.ToString("C")})";
+            return $"{this.Artist}: {this.Title} ({this.Price.ToString("C")})";
         }
 
     }

src/MahApps.Metro.Samples/MahApps.Metro.Demo/Models/Artist.cs

@@ -31,9 +31,13 @@ public List<Album>? Albums
             set => this.Set(ref this._albums, value);
         }
 
+#if NET5_0_OR_GREATER || NETCOREAPP
+        public override string? ToString()
+#else
         public override string ToString()
+#endif
         {
-            return Name;
+            return this.Name ?? base.ToString();
         }
     }
 }

src/MahApps.Metro.Samples/MahApps.Metro.Demo/Models/Genre.cs

@@ -38,9 +38,13 @@ public List<Album>? Albums
             set => this.Set(ref this._albums, value);
         }
 
+#if NET5_0_OR_GREATER || NETCOREAPP
+        public override string? ToString()
+#else
         public override string ToString()
+#endif
         {
-            return Name;
+            return this.Name ?? base.ToString();
         }
     }
 }

src/MahApps.Metro.Samples/MahApps.Metro.Demo/Models/ObjectParser.cs

@@ -14,13 +14,18 @@ public class ObjectParser : IParseStringToObject
         private readonly MainWindowViewModel _mainWindowViewModel;
         private readonly IDialogCoordinator _dialogCoordinator;
 
-        public ObjectParser (MainWindowViewModel mainWindowViewModel, IDialogCoordinator dialogCoordinator)
+        public ObjectParser(MainWindowViewModel mainWindowViewModel, IDialogCoordinator dialogCoordinator)
         {
             this._mainWindowViewModel = mainWindowViewModel;
             this._dialogCoordinator = dialogCoordinator;
         }
-
-        public bool TryCreateObjectFromString(string input, out object result, CultureInfo culture = null, string stringFormat = null, Type elementType = null)
+
+        /// <inheritdoc />
+        public bool TryCreateObjectFromString(string? input,
+                                              out object? result,
+                                              CultureInfo? culture = null,
+                                              string? stringFormat = null,
+                                              Type? elementType = null)
         {
             if (string.IsNullOrWhiteSpace(input))
             {
@@ -29,15 +34,15 @@ public bool TryCreateObjectFromString(string input, out object result, CultureIn
             }
 
             MetroDialogSettings dialogSettings = new MetroDialogSettings
-            {
-                AffirmativeButtonText = "Yes",
-                NegativeButtonText = "No",
-                DefaultButtonFocus = MessageDialogResult.Affirmative
-            };
+                                                 {
+                                                     AffirmativeButtonText = "Yes",
+                                                     NegativeButtonText = "No",
+                                                     DefaultButtonFocus = MessageDialogResult.Affirmative
+                                                 };
 
-            if (this._dialogCoordinator.ShowModalMessageExternal(this._mainWindowViewModel, "Add Animal", $"Do you want to add \"{input}\" to the animals list?",  MessageDialogStyle.AffirmativeAndNegative, dialogSettings) == MessageDialogResult.Affirmative)
+            if (this._dialogCoordinator.ShowModalMessageExternal(this._mainWindowViewModel, "Add Animal", $"Do you want to add \"{input}\" to the animals list?", MessageDialogStyle.AffirmativeAndNegative, dialogSettings) == MessageDialogResult.Affirmative)
             {
-                result = input.Trim();
+                result = input!.Trim();
                 return true;
             }
             else
@@ -47,4 +52,4 @@ public bool TryCreateObjectFromString(string input, out object result, CultureIn
             }
         }
     }
-}
+}

src/MahApps.Metro/Controls/Helper/BindingHelper.cs

@@ -37,7 +37,7 @@ private static readonly DependencyProperty DummyTextProperty
         /// <param name="source">the object to evaluate</param>
         /// <param name="expression">the binding expression to evaluate</param>
         /// <returns>the result of the <see cref="Binding"/></returns>
-        public static object Eval(object source, string expression)
+        public static object? Eval(object? source, string? expression)
         {
             Binding binding = new Binding(expression) { Source = source };
             return Eval(binding);
@@ -50,7 +50,7 @@ public static object Eval(object source, string expression)
         /// <param name="expression">the binding expression to evaluate</param>
         /// <param name="format">the string format to use</param>
         /// <returns>the result of the <see cref="Binding"/></returns>
-        public static object Eval(object source, string expression, string format)
+        public static object? Eval(object? source, string? expression, string? format)
         {
             Binding binding = new Binding(expression) { Source = source, StringFormat = format };
             return Eval(binding);
@@ -62,7 +62,7 @@ public static object Eval(object source, string expression, string format)
         /// <param name="binding">The <see cref="Binding"/> to evaluate</param>
         /// <param name="source">the object to evaluate</param>
         /// <returns></returns>
-        public static object Eval(Binding binding, object source)
+        public static object? Eval(Binding? binding, object? source)
         {
             if (binding is null)
             {
@@ -85,6 +85,7 @@ public static object Eval(Binding binding, object source)
                                      StringFormat = binding.StringFormat,
                                      TargetNullValue = binding.TargetNullValue
                                  };
+
             return Eval(newBinding);
         }
 
@@ -94,8 +95,13 @@ public static object Eval(Binding binding, object source)
         /// <param name="binding">The <see cref="Binding"/> to evaluate</param>
         /// <param name="dependencyObject">optional: The <see cref="DependencyObject"/> to evaluate</param>
         /// <returns>The resulting object</returns>
-        public static object Eval(Binding binding, DependencyObject dependencyObject)
+        public static object? Eval(Binding? binding, DependencyObject? dependencyObject)
         {
+            if (binding is null)
+            {
+                throw new ArgumentNullException(nameof(binding));
+            }
+
             dependencyObject ??= new DependencyObject();
 
             if (string.IsNullOrEmpty(binding.StringFormat))
@@ -115,7 +121,7 @@ public static object Eval(Binding binding, DependencyObject dependencyObject)
         /// </summary>
         /// <param name="binding">The <see cref="Binding"/> to evaluate</param>
         /// <returns>The resulting object</returns>
-        public static object Eval(Binding binding)
+        public static object? Eval(Binding? binding)
         {
             return Eval(binding, null);
         }

src/MahApps.Metro/Controls/Helper/TextBoxHelper.cs

@@ -1109,11 +1109,11 @@ public static void ButtonClicked(object sender, RoutedEventArgs e)
                         switch (multiSelectionComboBox.SelectionMode)
                         {
                             case SelectionMode.Single:
-                                multiSelectionComboBox.SelectedItem = null;
+                                multiSelectionComboBox.SetCurrentValue(MultiSelectionComboBox.SelectedItemProperty, null);
                                 break;
                             case SelectionMode.Multiple:
                             case SelectionMode.Extended:
-                                multiSelectionComboBox.SelectedItems.Clear();
+                                multiSelectionComboBox.SelectedItems?.Clear();
                                 break;
                             default:
                                 throw new NotSupportedException("Unknown SelectionMode");
@@ -1135,7 +1135,6 @@ public static void ButtonClicked(object sender, RoutedEventArgs e)
                 {
                     colorPicker.SetCurrentValue(ColorPickerBase.SelectedColorProperty, null);
                 }
-
             }
         }
 

src/MahApps.Metro/Controls/MultiSelectionComboBox/AddedItemEventArgs.cs

@@ -1,9 +1,8 @@
-using System;
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
 using System.Collections;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 using System.Windows;
 
 namespace MahApps.Metro.Controls
@@ -16,32 +15,33 @@ public class AddedItemEventArgs : RoutedEventArgs
         /// <summary>
         /// Initializes a new instance of the <see cref="AddedItemEventArgs"/> class.
         /// </summary>
-        /// <param name="routedEvent">The AddedItemEvent/param>
+        /// <param name="routedEvent">The AddedItemEvent</param>
         /// <param name="source">The source object</param>
         /// <param name="addedItem">The added object</param>
         /// <param name="targetList">The target <see cref="IList"/> where the <see cref="AddedItem"/> should be added</param>
         public AddedItemEventArgs(RoutedEvent routedEvent,
-                                   object source,
-                                   object addedItem,
-                                   IList targetList) : base(routedEvent, source)
+                                  object source,
+                                  object? addedItem,
+                                  IList? targetList)
+            : base(routedEvent, source)
         {
-            AddedItem = addedItem;
-            TargetList = targetList;
+            this.AddedItem = addedItem;
+            this.TargetList = targetList;
         }
 
         /// <summary>
         /// Gets the added item
         /// </summary>
-        public object AddedItem { get; }
+        public object? AddedItem { get; }
 
         /// <summary>
         /// Gets the <see cref="IList"/> where the <see cref="AddedItem"/> was added to
         /// </summary>
-        public IList TargetList { get; }
+        public IList? TargetList { get; }
     }
 
     /// <summary>
     /// RoutedEventHandler used for the <see cref="MultiSelectionComboBox.AddedItemEvent"/>.
     /// </summary>
-    public delegate void AddedItemEventArgsHandler(object sender, AddedItemEventArgs args);
-}
+    public delegate void AddedItemEventArgsHandler(object? sender, AddedItemEventArgs args);
+}

src/MahApps.Metro/Controls/MultiSelectionComboBox/AddingItemEventArgs.cs

@@ -1,4 +1,8 @@
-using System;
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
 using System.Collections;
 using System.Globalization;
 using System.Windows;
@@ -13,7 +17,7 @@ public class AddingItemEventArgs : RoutedEventArgs
         /// <summary>
         /// Initializes a new instance of the <see cref="AddingItemEventArgs"/> class.
         /// </summary>
-        /// <param name="routedEvent">The AddingItemEvent/param>
+        /// <param name="routedEvent">The AddingItemEvent</param>
         /// <param name="source">The source object</param>
         /// <param name="input">The input string to parse</param>
         /// <param name="parsedObject">The parsed object</param>
@@ -25,39 +29,40 @@ public class AddingItemEventArgs : RoutedEventArgs
         /// <param name="parser">The used parser</param>
         public AddingItemEventArgs(RoutedEvent routedEvent,
                                    object source,
-                                   string input,
-                                   object parsedObject,
+                                   string? input,
+                                   object? parsedObject,
                                    bool accepted,
-                                   IList targetList,
-                                   Type targetType,
-                                   string stringFormat,
+                                   IList? targetList,
+                                   Type? targetType,
+                                   string? stringFormat,
                                    CultureInfo culture,
-                                   IParseStringToObject parser): base(routedEvent, source)
+                                   IParseStringToObject? parser)
+            : base(routedEvent, source)
         {
-            Input = input;
-            ParsedObject = parsedObject;
-            Accepted = accepted;
-            TargetList = targetList;
-            TargetType = targetType;
-            StringFormat = stringFormat;
-            Culture = culture;
-            Parser = parser;
+            this.Input = input;
+            this.ParsedObject = parsedObject;
+            this.Accepted = accepted;
+            this.TargetList = targetList;
+            this.TargetType = targetType;
+            this.StringFormat = stringFormat;
+            this.Culture = culture;
+            this.Parser = parser;
         }
 
         /// <summary>
-        /// The Textinput to parse 
+        /// The text input to parse 
         /// </summary>
-        public string Input { get; } 
+        public string? Input { get; }
 
         /// <summary>
         /// Gets or sets the parsed object to add. You can override it
         /// </summary>
-        public object ParsedObject { get; set; }
+        public object? ParsedObject { get; set; }
 
         /// <summary>
         /// Gets the string format which can be used to control the <see cref="Parser"/>
         /// </summary>
-        public string StringFormat { get; }
+        public string? StringFormat { get; }
 
         /// <summary>
         /// Gets the culture which can be used to control the <see cref="Parser"/>
@@ -67,26 +72,26 @@ public AddingItemEventArgs(RoutedEvent routedEvent,
         /// <summary>
         /// Gets the <see cref="IParseStringToObject"/>-Instance which was used to parse the <see cref="Input"/> to the <see cref="ParsedObject"/>
         /// </summary>
-        public IParseStringToObject Parser { get; }
+        public IParseStringToObject? Parser { get; }
 
         /// <summary>
         /// Gets the target <see cref="Type"/> to which the <see cref="Input"/> should be converted to
         /// </summary>
-        public Type TargetType { get; }
+        public Type? TargetType { get; }
 
         /// <summary>
         /// Gets the <see cref="IList"/> where the <see cref="ParsedObject"/> should be added
         /// </summary>
-        public IList TargetList { get; }
+        public IList? TargetList { get; }
 
         /// <summary>
-        /// Gets or sets wether the <see cref="ParsedObject"/> is accepted and can be added
+        /// Gets or sets whether the <see cref="ParsedObject"/> is accepted and can be added
         /// </summary>
         public bool Accepted { get; set; }
     }
 
     /// <summary>
     /// RoutedEventHandler used for the <see cref="MultiSelectionComboBox.AddingItemEvent"/>.
     /// </summary>
-    public delegate void AddingItemEventArgsHandler(object sender, AddingItemEventArgs args);
-}
+    public delegate void AddingItemEventArgsHandler(object? sender, AddingItemEventArgs args);
+}