Add Count Distinct test

Author: mythz

src/ServiceStack.OrmLite/OrmLiteReadCommandExtensions.cs

@@ -505,7 +505,8 @@ internal static List<T> SelectNonDefaults<T>(this IDbCommand dbCmd, string sql,
 
         internal static IEnumerable<T> SelectLazy<T>(this IDbCommand dbCmd, string sql, IEnumerable<IDbDataParameter> sqlParams)
         {
-            foreach (var p in dbCmd.SetParameters(sqlParams).SelectLazy<T>(sql)) yield return p;
+            foreach (var p in dbCmd.SetParameters(sqlParams).SelectLazy<T>(sql))
+                yield return p;
         }
 
         internal static IEnumerable<T> SelectLazy<T>(this IDbCommand dbCmd, string sql, object anonType = null)

tests/ServiceStack.OrmLite.Tests/UseCase/ArtistTrackSqlExpressions.cs

@@ -60,5 +60,17 @@ public void Can_Select_joined_table_with_Alias()
                 Assert.That(tracksByYear.Map(x => x.Value).Sum(), Is.EqualTo(8));
             }
         }
+
+        [Test]
+        public void Can_Count_Distinct()
+        {
+            using (var db = CreateArtistAndTrackTablesWithData(OpenDbConnection()))
+            {
+                var differentArtistsCount = db.Scalar<int>(db.From<Track>()
+                    .Select(x => Sql.CountDistinct(x.ArtistId)));
+
+                Assert.That(differentArtistsCount, Is.EqualTo(4));
+            }
+        }
     }
 }