System.InvalidOperationException: 数据源的类型无效。
这个错误的原因是什么？
sqlApp1 查询结果是 select pono from po_approver where pono='00000001'

异常详细信息: System.InvalidOperationException: 数据源的类型无效。它必须是 IListSource、IEnumerable 或 IDataSource。

源错误: 


行 198:            GridView child = (GridView)e.Row.FindControl("gvChild");
行 199:
行 200:            child.DataSource =myapp1;
行 201:            child.DataBind();

 
 protected void gvParent_RowDataBound(object sender, GridViewRowEventArgs e)
    {
       if (e.Row.RowType == DataControlRowType.DataRow)
        {
            string sqlApp1 = "select pono from po_approver where pono='" + e.Row.Cells[2].Text+"' ";  
            MySqlCommand mySqlApp1 = new MySqlCommand(sqlApp1, myConnection);
            MySqlDataAdapter myapp1 = new MySqlDataAdapter(mySqlApp1);
           
            DataSet myap1 = new DataSet();
            myapp1.Fill(myap1);

            GridView child = (GridView)e.Row.FindControl("gvChild");

            child.DataSource =myapp1;
            child.DataBind();
            
        }
    }

[解决办法]
=》
child.DataSource =myap1;//是myap1而不是myapp1