Remove ORDER BY in RowCount expressions

Author: mythz

src/ServiceStack.OrmLite/Expressions/ReadExpressionCommandExtensions.cs

@@ -118,7 +118,9 @@ internal static long GetCount(this IDbCommand dbCmd, string sql)
 
         internal static long RowCount<T>(this IDbCommand dbCmd, SqlExpression<T> expression)
         {
-            return dbCmd.Scalar<long>(dbCmd.GetDialectProvider().ToRowCountStatement(expression.ToSelectStatement()));
+            //ORDER BY throws when used in subselects in SQL Server. Removing OrderBy() clause since it doesn't impact results
+            var countExpr = expression.Clone().OrderBy(); 
+            return dbCmd.Scalar<long>(dbCmd.GetDialectProvider().ToRowCountStatement(countExpr.ToSelectStatement()));
         }
 
         internal static long RowCount(this IDbCommand dbCmd, string sql)

tests/ServiceStack.OrmLite.Tests/Expression/SqlExpressionTests.cs

@@ -278,6 +278,29 @@ public void Can_do_ToCountStatement_with_SqlExpression_if_expression_has_groupby
             }
         }
 
+        [Test]
+        public void Can_get_RowCount_if_expression_has_OrderBy()
+        {
+            using (var db = OpenDbConnection())
+            {
+                db.DropAndCreateTable<LetterFrequency>();
+
+                db.Insert(new LetterFrequency { Letter = "A" });
+                db.Insert(new LetterFrequency { Letter = "B" });
+                db.Insert(new LetterFrequency { Letter = "B" });
+
+                var query = db.From<LetterFrequency>()
+                    .Select(x => x.Letter)
+                    .OrderBy(x => x.Id);
+
+                var rowCount = db.RowCount(query);
+                Assert.That(rowCount, Is.EqualTo(3));
+
+                rowCount = db.Select(query).Count;
+                Assert.That(rowCount, Is.EqualTo(3));
+            }
+        }
+
         [Test]
         public void Can_OrderBy_Fields_with_different_sort_directions()
         {