Updated to C# 6.

Launcher/App.config

@@ -1,6 +1,6 @@
-<?xml version="1.0" encoding="utf-8" ?>
+<?xml version="1.0" encoding="utf-8"?>
 <configuration>
     <startup>
-        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
+        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1"/>
     </startup>
-</configuration>
+</configuration>

Launcher/Databases/Database.cs

@@ -98,20 +98,17 @@ public DatabaseEntry this[string name]
 		/// <summary>
 		/// Gets the extension that marks files that store database entries in binary format.
 		/// </summary>
-		public string BinaryFileExtension { get; private set; }
+		public string BinaryFileExtension { get; }
 
 		/// <summary>
 		/// Gets the extension that marks files that store database entries in Xml format.
 		/// </summary>
-		public string XmlFileExtension { get; private set; }
+		public string XmlFileExtension { get; }
 
 		/// <summary>
 		/// Gets amount of entries in this database.
 		/// </summary>
-		public int Count
-		{
-			get { return this.TopLevelEntries.Count; }
-		}
+		public int Count => this.TopLevelEntries.Count;
 		#endregion
 		#region Events
 		#endregion
@@ -214,7 +211,7 @@ public void Save(string file)
 			}
 
 			string rawExtension = System.IO.Path.GetExtension(file);
-			string extension = rawExtension != null ? rawExtension.Substring(1) : null;
+			string extension = rawExtension?.Substring(1);
 
 			if (extension == this.BinaryFileExtension)
 			{
@@ -227,9 +224,7 @@ public void Save(string file)
 			else
 			{
 				throw new ArgumentException(
-					string.Format(
-								  "Database.Save: Unable to recognize file extension. Use [{0}] for Xml files and [{1}] for binaries. File that has been attempted to be saved: [{2}]. Extension is [{3}]",
-								  this.XmlFileExtension, this.BinaryFileExtension, file, extension));
+					$"Database.Save: Unable to recognize file extension. Use [{this.XmlFileExtension}] for Xml files and [{this.BinaryFileExtension}] for binaries. File that has been attempted to be saved: [{file}]. Extension is [{extension}]");
 			}
 		}
 		/// <summary>
@@ -246,7 +241,7 @@ public void Load(string file)
 			}
 
 			string rawExtension = System.IO.Path.GetExtension(file);
-			string extension = rawExtension != null ? rawExtension.Substring(1) : null;
+			string extension = rawExtension?.Substring(1);
 
 			if (extension == this.BinaryFileExtension)
 			{
@@ -259,9 +254,7 @@ public void Load(string file)
 			else
 			{
 				throw new ArgumentException(
-					string.Format(
-								  "Database.Load: Unable to recognize file extension. Use [{0}] for Xml files and [{1}] for binaries. File that has been attempted to be loaded: [{2}]. Recognized extension is [{3}]",
-								  this.XmlFileExtension, this.BinaryFileExtension, file, extension));
+					$"Database.Load: Unable to recognize file extension. Use [{this.XmlFileExtension}] for Xml files and [{this.BinaryFileExtension}] for binaries. File that has been attempted to be loaded: [{file}]. Recognized extension is [{extension}]");
 			}
 		}
 		#endregion
@@ -310,8 +303,7 @@ private void LoadBinary(string file)
 			{
 				if (br.ReadInt32() != DatabaseGlobals.BinaryDatabaseFileIdentifier)
 				{
-					throw new ArgumentException(string.Format(
-															  "Database.LoadBinary: Unable to recognize format of the file. File: {0}", file));
+					throw new ArgumentException($"Database.LoadBinary: Unable to recognize format of the file. File: {file}");
 				}
 				while (br.ReadInt32() != DatabaseGlobals.BinaryDatabaseFileEndMarker)
 				{
@@ -381,7 +373,7 @@ public class DatabaseEntry
 		/// <summary>
 		/// Gets sorted list of subentries.
 		/// </summary>
-		public SortedList<string, DatabaseEntry> SubEntries { get; private set; }
+		public SortedList<string, DatabaseEntry> SubEntries { get; }
 
 		/// <summary>
 		/// Provides read/write access to the subentry with specified name.
@@ -521,15 +513,13 @@ public void FromBinary(BinaryReader br)
 			{
 				EntryContentAttribute contentType =
 					DatabaseGlobals.RegisteredContentTypes.Find(x => x.TypeHash == br.ReadInt32());
-				if (contentType != null)
+
+				ConstructorInfo constructor =
+					contentType?.AttributedClass.GetConstructor(Type.EmptyTypes);
+				if (constructor != null)
 				{
-					ConstructorInfo constructor =
-						contentType.AttributedClass.GetConstructor(Type.EmptyTypes);
-					if (constructor != null)
-					{
-						this.Content = (DatabaseEntryContent)constructor.Invoke(null);
-						this.Content.FromBinary(br);
-					}
+					this.Content = (DatabaseEntryContent)constructor.Invoke(null);
+					this.Content.FromBinary(br);
 				}
 			}
 			// Read subentries.
@@ -617,16 +607,14 @@ public void FromXml(XmlElement element)
 				XmlElement contentElement = children[0];
 				EntryContentAttribute contentType =
 					DatabaseGlobals.RegisteredContentTypes.Find(x => x.TypeName == contentElement.Name);
-				if (contentType != null)
+
+				ConstructorInfo constructor =
+					contentType?.AttributedClass.GetConstructor(Type.EmptyTypes);
+				if (constructor != null)
 				{
-					ConstructorInfo constructor =
-						contentType.AttributedClass.GetConstructor(Type.EmptyTypes);
-					if (constructor != null)
-					{
-						this.Content = (DatabaseEntryContent)constructor.Invoke(null);
-						this.Content.FromXml(contentElement);
-						minimalAmountOfChildNodes++;
-					}
+					this.Content = (DatabaseEntryContent)constructor.Invoke(null);
+					this.Content.FromXml(contentElement);
+					minimalAmountOfChildNodes++;
 				}
 			}
 			if (element.ChildNodes.Count > minimalAmountOfChildNodes)
@@ -687,17 +675,17 @@ public sealed class EntryContentAttribute : Attribute
 		/// <summary>
 		/// Gets identifier of the class.
 		/// </summary>
-		public int TypeHash { get; private set; }
+		public int TypeHash { get; }
 
 		/// <summary>
 		/// Gets the name of the type of content.
 		/// </summary>
-		public string TypeName { get; private set; }
+		public string TypeName { get; }
 
 		/// <summary>
 		/// Gets class to which this attribute is applied.
 		/// </summary>
-		public Type AttributedClass { get; private set; }
+		public Type AttributedClass { get; }
 
 		/// <summary>
 		/// Creates new instance of <see cref="EntryContentAttribute"/> class.
@@ -717,9 +705,7 @@ public EntryContentAttribute(string name, Type type)
 			if (other != null)
 			{
 				throw new Exception(
-					string.Format(
-								  "Unable to register database entry content type with name that has the same hash value as one of the existing ones. New name = {0}, old name = {1}",
-								  this.TypeName, other.TypeName));
+					$"Unable to register database entry content type with name that has the same hash value as one of the existing ones. New name = {this.TypeName}, old name = {other.TypeName}");
 			}
 		}
 	}

Launcher/Extensions/PathUtils.cs

@@ -80,7 +80,7 @@ private static string EndWithBackSlashInternal(string folderPath)
 		{
 			return folderPath.EndsWith("\\")
 				? folderPath
-				: string.Format("{0}\\", folderPath);
+				: $"{folderPath}\\";
 		}
 	}
 }

Launcher/ExtraControls/ExtraFilesSelectionBox.Buttons.cs

@@ -44,12 +44,8 @@ private void ToggleFileSelection(object sender, RoutedEventArgs routedEventArgs)
 		private void MoveSelectedFileUp(object sender, RoutedEventArgs routedEventArgs)
 		{
 			SpinnerButtons buttons = sender as SpinnerButtons;
-			if (buttons == null)
-			{
-				return;
-			}
 
-			FileDesc fileDesc = buttons.DataContext as FileDesc;
+			FileDesc fileDesc = buttons?.DataContext as FileDesc;
 			if (fileDesc == null)
 			{
 				return;
@@ -70,12 +66,8 @@ private void MoveSelectedFileUp(object sender, RoutedEventArgs routedEventArgs)
 		private void MoveSelectedFileDown(object sender, RoutedEventArgs routedEventArgs)
 		{
 			SpinnerButtons buttons = sender as SpinnerButtons;
-			if (buttons == null)
-			{
-				return;
-			}
 
-			FileDesc fileDesc = buttons.DataContext as FileDesc;
+			FileDesc fileDesc = buttons?.DataContext as FileDesc;
 			if (fileDesc == null)
 			{
 				return;

Launcher/ExtraControls/ExtraFilesSelectionBox.xaml.cs

@@ -18,7 +18,6 @@ namespace Launcher
 	/// </summary>
 	public partial class ExtraFilesSelectionBox
 	{
-		private readonly ObservableCollection<object> fileSelection;
 		private List<string> selectedFiles;
 			/// <summary>
 		/// Gets the list of files that are currently selected.
@@ -52,16 +51,13 @@ public List<string> SelectedFiles
 		/// <summary>
 		/// Gets the observable collection that contains information about selected files.
 		/// </summary>
-		public ObservableCollection<object> FileSelection
-		{
-			get { return this.fileSelection; }
-		}
+		public ObservableCollection<object> FileSelection { get; }
 		/// <summary>
 		/// Creates a user control.
 		/// </summary>
 		public ExtraFilesSelectionBox()
 		{
-			this.fileSelection = new ObservableCollection<object>();
+			this.FileSelection = new ObservableCollection<object>();
 
 			this.InitializeComponent();
 
@@ -83,11 +79,11 @@ private void UpdatedSelectedFiles(object sender, NotifyCollectionChangedEventArg
 
 		private void ClearSelection()
 		{
-			foreach (FileDesc file in this.fileSelection.OfType<FileDesc>())
+			foreach (FileDesc file in this.FileSelection.OfType<FileDesc>())
 			{
 				file.Selected = false;
 			}
-			this.fileSelection.Clear();
+			this.FileSelection.Clear();
 		}
 		private void RemoveUnavailableSelection(object sender, NotifyCollectionChangedEventArgs args)
 		{
@@ -97,16 +93,16 @@ private void RemoveUnavailableSelection(object sender, NotifyCollectionChangedEv
 				case NotifyCollectionChangedAction.Replace:
 				case NotifyCollectionChangedAction.Reset:
 
-					for (int i = 0; i < this.fileSelection.Count; i++)
+					for (int i = 0; i < this.FileSelection.Count; i++)
 					{
-						FileDesc file = this.fileSelection[i] as FileDesc;
+						FileDesc file = this.FileSelection[i] as FileDesc;
 
 						Debug.Assert(file != null, "file != null");
 
 						if (!ExtraFilesLookUp.LoadableFiles.Contains(file))
 						{
 							file.Selected = false;
-							this.fileSelection.RemoveAt(i--);
+							this.FileSelection.RemoveAt(i--);
 						}
 					}
 

Launcher/ExtraControls/IwadComboBox.cs

@@ -25,7 +25,7 @@ public class IwadComboBox : ComboBox
 		/// <summary>
 		/// Gets the collection of available IWAD files.
 		/// </summary>
-		public ObservableCollection<IwadFile> Files { get; private set; }
+		public ObservableCollection<IwadFile> Files { get; }
 		/// <summary>
 		/// Creates a new instance of this type.
 		/// </summary>

Launcher/ExtraControls/NumericUpDown.cs

@@ -264,7 +264,7 @@ public override void OnApplyTemplate()
 			this.Loaded += (sender, args) =>
 			{
 				this.valueIsCommited = true;
-				this.valueBox.Text = this.Value == null ? "" : this.Value.ToString();
+				this.valueBox.Text = this.Value?.ToString() ?? "";
 
 				this.UpdateButtons();
 			};
@@ -402,7 +402,7 @@ private void CommitText(string value)
 		protected virtual void OnValueChanged(int? oldvalue, int? newvalue)
 		{
 			var handler = this.ValueChanged;
-			if (handler != null) handler(this, oldvalue, newvalue);
+			handler?.Invoke(this, oldvalue, newvalue);
 		}
 		private void UpdateButtons()
 		{

Launcher/ExtraControls/SpinnerButton.cs

@@ -47,7 +47,8 @@ public PointCollection Geometry
 		}
 		static SpinnerButton()
 		{
-			DefaultStyleKeyProperty.OverrideMetadata(typeof(SpinnerButton), new FrameworkPropertyMetadata(typeof(SpinnerButton)));
+			DefaultStyleKeyProperty.OverrideMetadata(typeof(SpinnerButton),
+													 new FrameworkPropertyMetadata(typeof(SpinnerButton)));
 		}
 	}
 }

Launcher/ExtraControls/SpinnerButtons.cs

@@ -140,7 +140,7 @@ public override void OnApplyTemplate()
 		protected virtual void OnClickUp(RoutedEventArgs e)
 		{
 			var handler = this.ClickUp;
-			if (handler != null) handler(this, e);
+			handler?.Invoke(this, e);
 		}
 		/// <summary>
 		/// Raises <see cref="ClickDown"/> event.
@@ -149,7 +149,7 @@ protected virtual void OnClickUp(RoutedEventArgs e)
 		protected virtual void OnClickDown(RoutedEventArgs e)
 		{
 			var handler = this.ClickDown;
-			if (handler != null) handler(this, e);
+			handler?.Invoke(this, e);
 		}
 		#endregion
 	}

Launcher/ExtraControls/TextBoxButton.cs

@@ -12,7 +12,8 @@ public class TextBoxButton : Button
 	{
 		static TextBoxButton()
 		{
-			DefaultStyleKeyProperty.OverrideMetadata(typeof(TextBoxButton), new FrameworkPropertyMetadata(typeof(TextBoxButton)));
+			DefaultStyleKeyProperty.OverrideMetadata(typeof(TextBoxButton),
+													 new FrameworkPropertyMetadata(typeof(TextBoxButton)));
 		}
 	}
 }

Launcher/ExtraWindows/Directories.xaml

@@ -68,7 +68,6 @@
 				 ItemContainerStyle="{StaticResource DirectoryItem}"
 				 Background="{DynamicResource {x:Static SystemColors.AppWorkspaceBrushKey}}"
 				 BorderThickness="0" HorizontalContentAlignment="Stretch"
-				 ItemTemplate="{StaticResource DirectoryLineTemplate}">
-		</ListBox>
+				 ItemTemplate="{StaticResource DirectoryLineTemplate}" />
 	</ScrollViewer>
 </Window>