Fix Order By for composite property projection in Criteria

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

@@ -367,5 +367,35 @@ public async Task HqlInClauseSubquery_ForEntityAsync()
 				Assert.That(results.Count, Is.EqualTo(2));
 			}
 		}
+
+		//NH-2926 (GH-1103)
+		[Test]
+		public async Task QueryOverOrderByAndWhereWithIdProjectionDoesntThrowAsync()
+		{
+			// 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())
+								.Where(Restrictions.Eq(Projections.Id(), id))
+								.OrderBy(Projections.Id()).Desc.ListAsync<Id>());
+				Assert.That(results.Count, Is.EqualTo(1));
+			}
+		}
 	}
 }

src/NHibernate.Test/CompositeId/ClassWithCompositeIdFixture.cs

@@ -356,5 +356,35 @@ public void HqlInClauseSubquery_ForEntity()
 				Assert.That(results.Count, Is.EqualTo(2));
 			}
 		}
+
+		//NH-2926 (GH-1103)
+		[Test]
+		public void QueryOverOrderByAndWhereWithIdProjectionDoesntThrow()
+		{
+			// 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())
+								.Where(Restrictions.Eq(Projections.Id(), id))
+								.OrderBy(Projections.Id()).Desc.List<Id>();
+				Assert.That(results.Count, Is.EqualTo(1));
+			}
+		}
 	}
 }

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

@@ -1,8 +1,7 @@
 using System;
-using System.Text;
-using NHibernate.Criterion;
 using NHibernate.Engine;
 using NHibernate.SqlCommand;
+using NHibernate.SqlTypes;
 
 namespace NHibernate.Criterion
 {
@@ -38,43 +37,54 @@ public Order(string propertyName, bool ascending)
 		/// </summary>
 		public virtual SqlString ToSqlString(ICriteria criteria, ICriteriaQuery criteriaQuery)
 		{
-			if (projection != null)
-			{
-				SqlString produced = projection.ToSqlString(criteria, 0, criteriaQuery);
-				SqlString truncated = SqlStringHelper.RemoveAsAliasesFromSql(produced);
-				return new SqlString(truncated, ascending ? " asc" : " desc");
-			}
-
-			string[] columns = criteriaQuery.GetColumnAliasesUsingProjection(criteria, propertyName);
-			Type.IType type = criteriaQuery.GetTypeUsingProjection(criteria, propertyName);
+			var columnsOrAliases = GetColumnsOrAliases(criteria, criteriaQuery);
+			var sqlTypes = ignoreCase ? SqlTypes(criteria, criteriaQuery) : null;
 
-			StringBuilder fragment = new StringBuilder();
-			ISessionFactoryImplementor factory = criteriaQuery.Factory;
-			for (int i = 0; i < columns.Length; i++)
+			var fragment = new SqlStringBuilder();
+			var factory = criteriaQuery.Factory;
+			for (var i = 0; i < columnsOrAliases.Length; i++)
 			{
-				bool lower = ignoreCase && IsStringType(type.SqlTypes(factory)[i]);
-
+				var lower = sqlTypes != null && IsStringType(sqlTypes[i]);
 				if (lower)
 				{
-					fragment.Append(factory.Dialect.LowercaseFunction)
-						.Append("(");
+					fragment
+						.Add(factory.Dialect.LowercaseFunction)
+						.Add("(");
 				}
-				fragment.Append(columns[i]);
+
+				fragment.AddObject(columnsOrAliases[i]);
 
 				if (lower)
 				{
-					fragment.Append(")");
+					fragment.Add(")");
 				}
 
-				fragment.Append(ascending ? " asc" : " desc");
+				fragment.Add(ascending ? " asc" : " desc");
 
-				if (i < columns.Length - 1)
+				if (i < columnsOrAliases.Length - 1)
 				{
-					fragment.Append(", ");
+					fragment.Add(", ");
 				}
 			}
 
-			return new SqlString(fragment.ToString());
+			return fragment.ToSqlString();
+		}
+
+		private object[] GetColumnsOrAliases(ICriteria criteria, ICriteriaQuery criteriaQuery)
+		{
+			var propName = propertyName ?? (projection as IPropertyProjection)?.PropertyName;
+			return propName != null
+				? criteriaQuery.GetColumnAliasesUsingProjection(criteria, propName)
+				: (object[]) CriterionUtil.GetColumnNamesUsingProjection(projection, criteriaQuery, criteria);
+		}
+
+		private SqlType[] SqlTypes(ICriteria criteria, ICriteriaQuery criteriaQuery)
+		{
+			var type = projection == null
+				? criteriaQuery.GetTypeUsingProjection(criteria, propertyName)
+				: projection.GetTypes(criteria, criteriaQuery)[0];
+
+			return type.SqlTypes(criteriaQuery.Factory);
 		}
 
 		public override string ToString()