当我尝试将数据从gridview填充到文本框时获取异常

Question

我得到的例外：

  

指数超出范围。必须是非负的且小于的大小   采集。参数名称：index

protected void gv_RowCommand(object sender, GridViewCommandEventArgs e)
{
    try
    {
        LoadData();
        if (e.CommandName == "Select")
        {
            var rowId = Convert.ToChar(e.CommandArgument);
            var hf = (HiddenField)((GridView)e.CommandSource).Rows[rowId].FindControl("hfKey");
            var AccountNo = String.Format(hf.Value);