Fix Order By for composite property projection in Criteria

Author: bahusoid

src/NHibernate.Test/Async/CompositeId/ClassWithCompositeIdFixture.cs

@@ -239,5 +239,33 @@ public async Task HqlAsync()
 				Assert.AreEqual(1, results.Count);
 			}
 		}
+
+		//NH-2926 (GH-1103)
+		[Test]
+		public async Task QueryOverOrderByIdProjectionDoesntThrowAsync()
+		{
+			// insert the new objects
+			using (ISession s = OpenSession())
+			using (ITransaction t = s.BeginTransaction())
+			{
+				ClassWithCompositeId theClass = new ClassWithCompositeId(id);
+				theClass.OneProperty = 5;
+
+				ClassWithCompositeId theSecondClass = new ClassWithCompositeId(secondId);
+				theSecondClass.OneProperty = 10;
+
+				await (s.SaveAsync(theClass));
+				await (s.SaveAsync(theSecondClass));
+
+				await (t.CommitAsync());
+			}
+
+			using (ISession s = OpenSession())
+			{
+				var results = await (s.QueryOver<ClassWithCompositeId>().Select(Projections.Id()).OrderBy(Projections.Id()).Desc.ListAsync<Id>());
+				Assert.That(results.Count, Is.EqualTo(2));
+			}
+		}
+
 	}
 }

src/NHibernate.Test/CompositeId/ClassWithCompositeIdFixture.cs

@@ -228,5 +228,33 @@ public void Hql()
 				Assert.AreEqual(1, results.Count);
 			}
 		}
+
+		//NH-2926 (GH-1103)
+		[Test]
+		public void QueryOverOrderByIdProjectionDoesntThrow()
+		{
+			// insert the new objects
+			using (ISession s = OpenSession())
+			using (ITransaction t = s.BeginTransaction())
+			{
+				ClassWithCompositeId theClass = new ClassWithCompositeId(id);
+				theClass.OneProperty = 5;
+
+				ClassWithCompositeId theSecondClass = new ClassWithCompositeId(secondId);
+				theSecondClass.OneProperty = 10;
+
+				s.Save(theClass);
+				s.Save(theSecondClass);
+
+				t.Commit();
+			}
+
+			using (ISession s = OpenSession())
+			{
+				var results = s.QueryOver<ClassWithCompositeId>().Select(Projections.Id()).OrderBy(Projections.Id()).Desc.List<Id>();
+				Assert.That(results.Count, Is.EqualTo(2));
+			}
+		}
+
 	}
 }

src/NHibernate/Criterion/CriterionUtil.cs

@@ -46,6 +46,11 @@ public static SqlString[] GetColumnNamesForSimpleExpression(
 
 		internal static SqlString[] GetColumnNamesUsingProjection(IProjection projection, ICriteriaQuery criteriaQuery, ICriteria criteria)
 		{
+			if (projection is IPropertyProjection propertyProjection)
+			{
+				return GetColumnNamesUsingPropertyName(criteriaQuery, criteria, propertyProjection.PropertyName);
+			}
+
 			SqlString sqlString = projection.ToSqlString(criteria, 
 				criteriaQuery.GetIndexForAlias(),
 				criteriaQuery);

src/NHibernate/Criterion/IdentifierProjection.cs

@@ -1,12 +1,12 @@
 using System;
+using NHibernate.Persister.Entity;
 using NHibernate.SqlCommand;
 using NHibernate.Type;
-using NHibernate.Util;
 
 namespace NHibernate.Criterion
 {
 	[Serializable]
-	public class IdentifierProjection : SimpleProjection
+	public class IdentifierProjection : SimpleProjection, IPropertyProjection
 	{
 		private bool grouped;
 
@@ -21,7 +21,7 @@ protected internal IdentifierProjection() : this(false)
 
 		public override string ToString()
 		{
-			return "id";
+			return PropertyName;
 		}
 
 		public override IType[] GetTypes(ICriteria criteria, ICriteriaQuery criteriaQuery)
@@ -66,5 +66,7 @@ public override SqlString ToGroupSqlString(ICriteria criteria, ICriteriaQuery cr
 			}
 			return new SqlString(string.Join(",", criteriaQuery.GetIdentifierColumns(criteria)));
 		}
+
+		public string PropertyName => EntityPersister.EntityID;
 	}
 }

src/NHibernate/Criterion/Order.cs

@@ -38,18 +38,8 @@ public Order(string propertyName, bool ascending)
 		/// </summary>
 		public virtual SqlString ToSqlString(ICriteria criteria, ICriteriaQuery criteriaQuery)
 		{
-			if (projection != null)
-			{
-				SqlString sb = SqlString.Empty;
-				SqlString produced = this.projection.ToSqlString(criteria, 0, criteriaQuery);
-				SqlString truncated = SqlStringHelper.RemoveAsAliasesFromSql(produced);
-				sb = sb.Append(truncated);
-				sb = sb.Append(ascending ? " asc" : " desc");
-				return sb;
-			}
-
-			string[] columns = criteriaQuery.GetColumnAliasesUsingProjection(criteria, propertyName);
-			Type.IType type = criteriaQuery.GetTypeUsingProjection(criteria, propertyName);
+			SqlString[] columns = CriterionUtil.GetColumnNames(propertyName, projection, criteriaQuery, criteria);
+			Type.IType type = projection?.GetTypes(criteria, criteriaQuery)[0] ?? criteriaQuery.GetTypeUsingProjection(criteria, propertyName);
 
 			StringBuilder fragment = new StringBuilder();
 			ISessionFactoryImplementor factory = criteriaQuery.Factory;