Synchronization code

Src/Asp.NetCore2/SqlSugar/ExpressionsToSql/ResolveItems/MethodCallExpressionResolve.cs

@@ -226,7 +226,7 @@ namespace SqlSugar
                         var member = (item as MemberExpression);
                         if (member.Member.Name == "HasValue") 
                         {
-                            newItem = ExpressionBuilderHelper.CreateExpression(member.Expression, Expression.Constant(null), ExpressionType.Equal);
+                            newItem = ExpressionBuilderHelper.CreateExpression(member.Expression, Expression.Constant(null), ExpressionType.NotEqual);
                         }
                         AppendItem(parameter, name, new List<Expression>() { newItem}, model, newItem);
                     }

Src/Asp.NetCore2/SqlSugar/Utilities/ExpressionBuilderHelper.cs

@@ -44,6 +44,10 @@ namespace SqlSugar
             {
                 return Expression.Equal(left, Expression.Convert(value, left.Type));
             }
+            else if (type == ExpressionType.NotEqual)
+            {
+                return Expression.NotEqual(left, Expression.Convert(value, left.Type));
+            }
             else 
             {
                 //Not implemented, later used in writing