Introduced "Convert interface to abstract class" context action.

src/AddIns/BackendBindings/CSharpBinding/Project/CSharpBinding.addin

@@ -317,6 +317,7 @@
 		<Class class="CSharpBinding.Refactoring.MoveTypeToFileContextAction" />
 		<Class class="CSharpBinding.Refactoring.RenameFileToMatchTypeNameContextAction" />
 		<Class class="CSharpBinding.Refactoring.ParamRangeCheckContextAction" />
+		<Class class="CSharpBinding.Refactoring.ConvertInterfaceToAbstractClassContextAction" />
 	</Path>
 	
 	<Path name = "/SharpDevelop/Workbench/DisplayBindings">

src/AddIns/BackendBindings/CSharpBinding/Project/CSharpBinding.csproj

@@ -88,6 +88,7 @@
     <Compile Include="Src\FormsDesigner\SecondaryDisplayBinding.cs" />
     <Compile Include="Src\Parser\FoldingVisitor.cs" />
     <Compile Include="Src\Refactoring\AbstractInlineRefactorDialog.cs" />
+    <Compile Include="Src\Refactoring\ConvertInterfaceToAbstractClassContextAction.cs" />
     <Compile Include="Src\Refactoring\CreateProperties.cs" />
     <Compile Include="Src\Refactoring\CreatePropertiesCommand.cs" />
     <Compile Include="Src\Refactoring\CreatePropertiesDialog.xaml.cs">

src/AddIns/BackendBindings/CSharpBinding/Project/Src/Refactoring/ConvertInterfaceToAbstractClassContextAction.cs

@@ -0,0 +1,62 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using ICSharpCode.NRefactory.CSharp;
+using ICSharpCode.NRefactory.CSharp.Refactoring;
+using ICSharpCode.SharpDevelop.Refactoring;
+using CSharpBinding.Parser;
+
+namespace CSharpBinding.Refactoring
+{
+	[ContextAction("Convert interface to abstract class", Description = "Converts an interface to a class with abstract members.")]
+	public class ConvertInterfaceToAbstractClassContextAction : ContextAction
+	{
+		public override async Task<bool> IsAvailableAsync(EditorRefactoringContext context, CancellationToken cancellationToken)
+		{
+			SyntaxTree st = await context.GetSyntaxTreeAsync().ConfigureAwait(false);
+			Identifier identifier = (Identifier) st.GetNodeAt(context.CaretLocation, node => node.Role == Roles.Identifier);
+			if (identifier == null)
+				return false;
+			TypeDeclaration typeDeclaration = identifier.Parent as TypeDeclaration;
+			return (typeDeclaration != null) && (typeDeclaration.ClassType == ClassType.Interface);
+		}
+
+		public override void Execute(EditorRefactoringContext context)
+		{
+			CSharpFullParseInformation parseInformation = context.GetParseInformation() as CSharpFullParseInformation;
+			if (parseInformation != null) {
+				SyntaxTree st = parseInformation.SyntaxTree;
+				Identifier identifier = (Identifier) st.GetNodeAt(context.CaretLocation, node => node.Role == Roles.Identifier);
+				if (identifier == null)
+					return;
+				TypeDeclaration interfaceTypeDeclaration = identifier.Parent as TypeDeclaration;
+				if (interfaceTypeDeclaration != null) {
+					// Generate abstract class from interface and abstract members from interface members
+					TypeDeclaration abstractClassTypeNode = (TypeDeclaration) interfaceTypeDeclaration.Clone();
+					abstractClassTypeNode.ClassType = ClassType.Class;
+					abstractClassTypeNode.Modifiers |= Modifiers.Abstract;
+					foreach (var entity in abstractClassTypeNode.Children.OfType<EntityDeclaration>()) {
+						entity.Modifiers |= Modifiers.Abstract | Modifiers.Public;
+					}
+					
+					var refactoringContext = SDRefactoringContext.Create(context.Editor, CancellationToken.None);
+					using (Script script = refactoringContext.StartScript()) {
+						// Replace interface node with node of abstract class
+						script.Replace(interfaceTypeDeclaration, abstractClassTypeNode);
+					}
+				}
+			}
+		}
+
+		public override string DisplayName
+		{
+			get {
+				return "Convert interface to abstract class";
+			}
+		}
+	}
+}