Do not convert simple LINQ method calls to LINQ expressions. Closes #1501.

ICSharpCode.Decompiler.Tests/TestCases/Pretty/ExpressionTrees.cs

@@ -625,16 +625,15 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			//no params
 			ToCode(X(), () => call(() => 42));
 			//one param
-			ToCode(X(), () => from x in new int[2] {
+			ToCode(X(), () => new int[2] {
 				37,
 				42
-			}
-			select x * 2);
+			}.Select((int x) => x * 2));
 			//two params
 			ToCode(X(), () => new int[2] {
-			37,
-			42
-		}.Select((int x, int i) => x * 2));
+				37,
+				42
+			}.Select((int x, int i) => x * 2));
 		}
 
 		public void CurriedLambda()
@@ -731,13 +730,12 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 
 		public void QuotedWithAnonymous()
 		{
-			ToCode(X(), () => (from o in new[] {
+			ToCode(X(), () => new[] {
 				new {
 					X = "a",
 					Y = "b"
 				}
-			}
-			select o.X + o.Y).Single());
+			}.Select(o => o.X + o.Y).Single());
 		}
 
 		public void StaticCall()

ICSharpCode.Decompiler.Tests/TestCases/Pretty/InitializerTests.cs

@@ -1468,9 +1468,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty.InitializerTests
 					DateTimeFormat = new DateTimeFormatInfo {
 						ShortDatePattern = "ddmmyy"
 					},
-					NumberFormat = (from format in source
-									where format.CurrencySymbol == "$"
-									select format).First()
+					NumberFormat = source.Where((NumberFormatInfo format) => format.CurrencySymbol == "$").First()
 				}
 			});
 		}

ICSharpCode.Decompiler/CSharp/Transforms/IntroduceQueryExpressions.cs

@@ -90,10 +90,11 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			if (mre == null || IsNullConditional(mre.Target))
 				return null;
 			switch (mre.MemberName) {
-				case "Select":
-					{
+				case "Select": {
 						if (invocation.Arguments.Count != 1)
 							return null;
+						if (!IsComplexQuery(mre))
+							return null;
 						ParameterDeclaration parameter;
 						Expression body;
 						if (MatchSimpleLambda(invocation.Arguments.Single(), out parameter, out body)) {
@@ -158,6 +159,8 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 					{
 						if (invocation.Arguments.Count != 1)
 							return null;
+						if (!IsComplexQuery(mre))
+							return null;
 						ParameterDeclaration parameter;
 						Expression body;
 						if (MatchSimpleLambda(invocation.Arguments.Single(), out parameter, out body)) {
@@ -175,6 +178,8 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 					{
 						if (invocation.Arguments.Count != 1)
 							return null;
+						if (!IsComplexQuery(mre))
+							return null;
 						ParameterDeclaration parameter;
 						Expression orderExpression;
 						if (MatchSimpleLambda(invocation.Arguments.Single(), out parameter, out orderExpression)) {
@@ -250,6 +255,11 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			}
 		}
 
+		static bool IsComplexQuery(MemberReferenceExpression mre)
+		{
+			return ((mre.Target is InvocationExpression && mre.Parent is InvocationExpression) || mre.Parent?.Parent is QueryClause);
+		}
+
 		QueryFromClause MakeFromClause(ParameterDeclaration parameter, Expression body)
 		{
 			QueryFromClause fromClause = new QueryFromClause {