GridView is not binding C#

我正在使用GridView并试图将数据绑定到此GridView，但我遇到了不寻常的问题，这是我的代码：

绑定GridView:的方法

private void BindDataSource()
    {
        SqlConnection con = new         SqlConnection(ConfigurationManager.ConnectionStrings["constr"].ConnectionString);
        string queryString6 = "";
        string items = "";
        if (lb_add_col.Items.Count > 0)
        {
            foreach (ListItem listItem in lb_add_col.Items)
            {
                if (listItem.Selected == true)
                {
                    items += listItem.Text + ",";
                }
            }
        }
        items = items.TrimEnd(',');
        queryString6 = "SELECT "+items+" from " +ddl_tables.Items[0].Text;
        System.Data.SqlClient.SqlCommand sqlCmd6 = new System.Data.SqlClient.SqlCommand(queryString6, con);
        System.Data.SqlClient.SqlDataAdapter dataAdapter6 = new System.Data.SqlClient.SqlDataAdapter(sqlCmd6);
        System.Data.DataSet dataSet6 = new System.Data.DataSet();
        dataAdapter6.Fill(dataSet6);
        string[] columns = items.Split(',');
        for (int i = 0; i < dataSet6.Tables[0].Rows.Count; i++)
        {
            order.Add(new Orders(columns.Contains("id") ? Convert.ToInt32(dataSet6.Tables[0].Rows[i]["id"]) : 0, columns.Contains("name") ? dataSet6.Tables
            [0].Rows[i]["name"].ToString() : "N/A", columns.Contains("month") ? dataSet6.Tables[0].Rows[i]["month"].ToString() : "N/A", columns.Contains("effiecency") ? Convert.ToInt32(dataSet6.Tables[0].Rows[i]
            ["effiecency"]) : 0, columns.Contains("latitude") ? Convert.ToInt32(dataSet6.Tables[0].Rows[i]["latitude"]) : 0, columns.Contains("longitude") ? Convert.ToInt32(dataSet6.Tables[0].Rows[i]
            ["longitude"]) : 0));
        }
        this.OrdersGrid.DataSource = order;
        this.OrdersGrid.DataBind();
    }

从上面的方法顺序显示数据，但GridView并没有绑定。

按钮点击我调用此方法的事件：

protected void btn_add_col_Click(object sender, EventArgs e)
    {
        Syncfusion.JavaScript.Models.Column sd;
        foreach (ListItem listItem in lb_add_col.Items)
        {
            if (listItem.Selected == true)
            {
                sd = new Syncfusion.JavaScript.Models.Column();
                if (listItem.Text == "id")
                {
                    sd.IsPrimaryKey = true;
                }
                sd.Field = listItem.Text;
                sd.HeaderText = listItem.Value;
                sd.Width = 90;
                sd.TextAlign = Syncfusion.JavaScript.TextAlign.Right;
                this.OrdersGrid.Columns.Add(sd);
            }
        }
        BindDataSource();
    }