--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/UnitTests/Linq/UserTests/UnknownSqlTest.cs	Thu Mar 27 21:46:09 2014 +0400
@@ -0,0 +1,42 @@
+using System;
+using System.Linq;
+
+using BLToolkit.Data.Linq;
+
+using NUnit.Framework;
+
+namespace Data.Linq.UserTests
+{
+	[TestFixture]
+	public class UnknownSqlTest : TestBase
+	{
+		enum ColumnDataType
+		{
+			Unknown = 0,
+			Text    = 1,
+		}
+
+		class CustomTableColumn
+		{
+			public int? DataTypeID { get; set; }
+		}
+
+		[Test]
+		public void Test()
+		{
+			using (var db = new TestDbManager())
+			{
+				var q = db.GetTable<CustomTableColumn>()
+					.Select(
+						x => new
+						{
+							DataType = Sql.AsSql(ColumnDataType.Unknown),
+						});
+
+				var sql = q.ToString();
+
+				Assert.That(sql, Is.Not.Contains("Unknown"));
+			}
+		}
+	}
+}