Create allow-multiple-instances option and its option page

ILSpy/CommandLineArguments.cs

@@ -18,6 +18,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Configuration;
 
 namespace ICSharpCode.ILSpy
 {

ILSpy/ILSpy.csproj

@@ -169,6 +169,10 @@
       <DependentUpon>DisplaySettingsPanel.xaml</DependentUpon>
       <SubType>Code</SubType>
     </Compile>
+    <Compile Include="Options\MiscSettings.cs" />
+    <Compile Include="Options\MiscSettingsPanel.xaml.cs">
+      <DependentUpon>MiscSettingsPanel.xaml</DependentUpon>
+    </Compile>
     <Compile Include="Options\OptionsDialog.xaml.cs">
       <DependentUpon>OptionsDialog.xaml</DependentUpon>
       <SubType>Code</SubType>
@@ -315,6 +319,10 @@
     <Page Include="OpenListDialog.xaml" />
     <Page Include="Options\DecompilerSettingsPanel.xaml" />
     <Page Include="Options\DisplaySettingsPanel.xaml" />
+    <Page Include="Options\MiscSettingsPanel.xaml">
+      <SubType>Designer</SubType>
+      <Generator>MSBuild:Compile</Generator>
+    </Page>
     <Page Include="Options\OptionsDialog.xaml" />
     <Page Include="SearchPane.xaml">
       <DependentUpon>SearchPane.cs</DependentUpon>

ILSpy/Options/MiscSettings.cs

@@ -0,0 +1,48 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Linq;
+using System.Text;
+
+namespace ICSharpCode.ILSpy.Options
+{
+	public class MiscSettings : INotifyPropertyChanged
+	{
+		bool allowMultipleInstances = false;
+
+		/// <summary>
+		/// Decompile anonymous methods/lambdas.
+		/// </summary>
+		public bool AllowMultipleInstances
+		{
+			get
+			{
+				return allowMultipleInstances;
+			}
+			set
+			{
+				if (allowMultipleInstances != value)
+				{
+					allowMultipleInstances = value;
+					OnPropertyChanged("AllowMultipleInstance");
+				}
+			}
+		}
+
+		#region INotifyPropertyChanged Implementation
+
+		public event PropertyChangedEventHandler PropertyChanged;
+
+		protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
+		{
+			PropertyChanged?.Invoke(this, e);
+		}
+
+		protected void OnPropertyChanged(string propertyName)
+		{
+			OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
+		}
+
+		#endregion
+	}
+}

ILSpy/Options/MiscSettingsPanel.xaml

@@ -0,0 +1,11 @@
+<UserControl x:Class="ICSharpCode.ILSpy.Options.MiscSettingsPanel"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+			 mc:Ignorable="d" 
+             d:DesignHeight="300" d:DesignWidth="300">
+	<StackPanel Margin="10">
+		<CheckBox IsChecked="{Binding AllowMultipleInstances}">Allow multiple instances</CheckBox>
+	</StackPanel>
+</UserControl>

ILSpy/Options/MiscSettingsPanel.xaml.cs

@@ -0,0 +1,56 @@
+using ICSharpCode.Decompiler;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Data;
+using System.Windows.Documents;
+using System.Windows.Input;
+using System.Windows.Media;
+using System.Windows.Media.Imaging;
+using System.Windows.Navigation;
+using System.Windows.Shapes;
+using System.Xml.Linq;
+
+namespace ICSharpCode.ILSpy.Options
+{
+	/// <summary>
+	/// Interaction logic for MiscSettingsPanel.xaml
+	/// </summary>
+	[ExportOptionPage(Title = "Misc", Order = 2)]
+	public partial class MiscSettingsPanel : UserControl, IOptionPage
+	{
+		public MiscSettingsPanel()
+		{
+			InitializeComponent();
+		}
+
+		public void Load(ILSpySettings settings)
+		{
+			this.DataContext = LoadDecompilerSettings(settings);
+		}
+
+		private MiscSettings LoadDecompilerSettings(ILSpySettings settings)
+		{
+			XElement e = settings["MiscSettings"];
+			MiscSettings s = new MiscSettings();
+			s.AllowMultipleInstances = (bool?)e.Attribute("allowMultipleInstance") ?? s.AllowMultipleInstances;
+			return s;
+		}
+
+		public void Save(XElement root)
+		{
+			MiscSettings s = (MiscSettings)this.DataContext;
+			XElement section = new XElement("MiscSettings");
+			section.SetAttributeValue("allowMultipleInstance", s.AllowMultipleInstances);
+
+			XElement existingElement = root.Element("MiscSettings");
+			if (existingElement != null)
+				existingElement.ReplaceWith(section);
+			else
+				root.Add(section);
+		}
+	}
+}