Add demo

Src/Asp.Net/AccessTest/Demo/DemoE_CodeFirst.cs

@@ -19,14 +19,21 @@ namespace OrmTest
                 InitKeyType = InitKeyType.Attribute,
                 IsAutoCloseConnection = true
             });
-            db.DbMaintenance.CreateDatabase(); 
+            //db.DbMaintenance.CreateDatabase(); 
             db.CodeFirst.InitTables(typeof(CodeFirstTable1));//Create CodeFirstTable1 
             db.Insertable(new CodeFirstTable1() { Name = "a", Text="a" }).ExecuteCommand();
             var list = db.Queryable<CodeFirstTable1>().ToList();
+            db.CodeFirst.InitTables<DateTimeTest2>();
+            db.Insertable(new DateTimeTest2() { }).ExecuteCommand();
             Console.WriteLine("#### CodeFirst end ####");
         }
     }
 
+    public class DateTimeTest2
+    {
+        [SugarColumn(IsNullable =true)]
+        public DateTime? dt { get; set; }
+    }
     public class CodeFirstTable1
     {
         [SugarColumn(IsIdentity = true, IsPrimaryKey = true)]

Src/Asp.Net/AccessTest/Program.cs

@@ -11,6 +11,7 @@ namespace OrmTest
         /// <param name="args"></param>
         static void Main(string[] args)
         {
+            DemoE_CodeFirst.Init();
             Demo0_SqlSugarClient.Init();
             Demo1_Queryable.Init();
             Demo2_Updateable.Init();