Fix #1439: Add DecompilerSettings.UseLambdaSyntax

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -1633,7 +1633,7 @@ namespace ICSharpCode.Decompiler.CSharp
 			if (ame.Parameters.Any(p => p.Type.IsNull)) {
 				// if there is an anonymous type involved, we are forced to use a lambda expression.
 				isLambda = true;
-			} else if (ame.Parameters.All(p => p.ParameterModifier == ParameterModifier.None)) {
+			} else if (settings.UseLambdaSyntax && ame.Parameters.All(p => p.ParameterModifier == ParameterModifier.None)) {
 				// otherwise use lambda only if an expression lambda is possible
 				isLambda = (body.Statements.Count == 1 && body.Statements.Single() is ReturnStatement);
 			}

ICSharpCode.Decompiler/DecompilerSettings.cs

@@ -54,6 +54,7 @@ namespace ICSharpCode.Decompiler
 			}
 			if (languageVersion < CSharp.LanguageVersion.CSharp3) {
 				anonymousTypes = false;
+				useLambdaSyntax = false;
 				objectCollectionInitializers = false;
 				automaticProperties = false;
 				extensionMethods = false;
@@ -148,6 +149,21 @@ namespace ICSharpCode.Decompiler
 			}
 		}
 
+		bool useLambdaSyntax = true;
+
+		/// <summary>
+		/// Use C# 3 lambda syntax if possible.
+		/// </summary>
+		public bool UseLambdaSyntax {
+			get { return useLambdaSyntax; }
+			set {
+				if (useLambdaSyntax != value) {
+					useLambdaSyntax = value;
+					OnPropertyChanged();
+				}
+			}
+		}
+
 		bool expressionTrees = true;
 
 		/// <summary>