gridview要点击两下修改才能正常触发

第一次点击是刷新，第二次才正确。我想做的是点击修改按钮后显示层，在层里对数据进行修改。
前台  aspx
----------------------------------------------------
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="View.aspx.cs" Inherits="htluwan_Xuanshou_View" %>
<%@ Register Assembly="MagicAjax" Namespace="MagicAjax.UI.Controls" TagPrefix="ajax" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>无标题页</title>
    <link href="../../htluwan/Xuanshou/css.css" rel="stylesheet" type="text/css" />
    <script language="javascript" type="text/javascript">
    function ShowInsertDialog()
    {
    document.getElementById("InsertDialog").style.display="";
    }
    function HideInsertDialog()
    {
    document.getElementById("InsertDialog").style.display="none";
    }
    function ShowMdfDialog()
    {
    document.getElementById("MdfDialog").style.display="";
    }
    function HideMdfDialog()
    {
    document.getElementById("MdfDialog").style.display="none";
    }
    function ShowPreDialog()
    {
    document.getElementById("PreDialog").style.display="";
    }
    function HidePreDialog()
    {
    document.getElementById("PreDialog").style.display="none";
    }
    </script>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /></head>
<body>
    <form id="form1" runat="server">
   <div style="height:50px;"></div> 
    <ajax:AjaxPanel ID="AjaxPanel1" runat="server" Width="100%">
<table id="MdfDialog" class="hideDiv" style="DISPLAY: none ; text-align:center; width:100%;">
<tr>
<td>
<div id="Div1" class="errorMsg">
<div id="Div2" class="errorTitle">参赛选手修改</div>
<div id="Div3" class="errorBody" style="width: 500px">
    <table>
    <tr>
    <td style="width:120px;"><div style="text-align:right;">选手姓名</div></td>
    <td style="text-align:left; width: 377px;"><asp:textbox id="txtMdfName" runat="server" width="140px"></asp:textbox></td>
    </tr>
    <tr>
    <td style="width: 120px">性别</td>
    <td style="text-align:left; width: 377px;">
    <asp:RadioButton id="RBMdfMan" runat="server" GroupName="Mdfsex" text="男"></asp:RadioButton>
    <asp:RadioButton id="RBMdfWoman" runat="server" GroupName="Mdfsex" text="女"></asp:RadioButton>
    </td>
    </tr>
    <tr>
    <td style="width: 120px">年龄</td>
    <td style="text-align:left; width: 377px;"><asp:textbox id="txtMdfAge" runat="server" width="80px"></asp:textbox></td>
    </tr>
    <tr>
    <td style="width: 120px">国籍</td>
    <td style="text-align:left; width: 377px;"><asp:TextBox id="txtMdfGuoji" runat="server" width="80px"></asp:TextBox></td>
    </tr>
    <tr>
    <td style="width: 120px">档案</td>
    <td style="text-align:left; width: 377px;"><textarea id="MdfContent" style="width:350px; height:100px;" runat="server"></textarea></td>
    </tr>
    <tr>
    <td style="width: 120px">选手照片</td>
    <td style="text-align:left; width: 377px;"><input type="file" name="inputpicture" /></td>
    </tr>
    <tr>
    <td colspan="2" style="height:14px;"></td>
    </tr>
    <tr>
    <td style="text-align:right; width: 120px;"><asp:Button id="MdfSubmitBtn" runat="server" text="确定" OnClick="MdfSubmitBtn_Click"/></td>
    <td style="text-align:left; width: 377px;"><asp:Button id="MdfReturnBtn" runat="server" text="取消" OnClick="MdfReturnBtn_Click"/>
    <asp:HiddenField ID="id" runat="server" />
    </td>
    </tr>
    </table>
</div>
</div>
</td>
</tr>
</table>
   <div style="text-align:left">
    <asp:GridView ID="GVXuanshou" runat="server" AllowPaging="True" AutoGenerateColumns="False" PageSize="20" Font-Size="9pt" BackColor="#E0E0E0" OnRowCommand="GVXuanshou_RowCommand" OnRowDataBound="GVXuanshou_RowDataBound" OnRowDeleting="GVXuanshou_RowDeleting" >
    <Columns>
    <asp:TemplateField HeaderText="选手国籍">
    <ItemTemplate><div style="text-align:center;">
    <%# DataBinder.Eval(Container.DataItem,"guoji") %>
    </div></ItemTemplate>
        <ItemStyle Width="60px" />
    </asp:TemplateField>
    <asp:TemplateField HeaderText="选手姓名">
    <ItemTemplate><div style="text-align:center;">
    <%# DataBinder.Eval(Container.DataItem,"name") %>
    </div></ItemTemplate>
        <ItemStyle Width="120px" />
    </asp:TemplateField>
    <asp:TemplateField HeaderText="选手性别">
    <ItemTemplate><div style="text-align:center;">
    <%# DataBinder.Eval(Container.DataItem,"sex") %>
    </div></ItemTemplate>
        <ItemStyle Width="60px" />
    </asp:TemplateField>
    <asp:TemplateField HeaderText="选手年龄">
    <ItemTemplate><div style="text-align:center;">
    <%# DataBinder.Eval(Container.DataItem,"age") %>
    </div></ItemTemplate>
        <ItemStyle Width="80px" />
    </asp:TemplateField>
    <asp:TemplateField HeaderText="操作">
    <ItemTemplate><div style="text-align:center;">
    <asp:Button ID="MdfBtn" runat="server" Text="修改" CommandArgument='<%# DataBinder.Eval(Container.DataItem,"id") %>' CommandName="mdf" />    &nbsp;&nbsp;
    <asp:Button ID="DeleteBtn" runat="server" Text="删除" CommandArgument='<%# DataBinder.Eval(Container.DataItem,"id") %>' CommandName="delete" />
    &nbsp;&nbsp;
    <asp:Button ID="PreBtn" runat="server" Text="预览" CommandArgument='<%# DataBinder.Eval(Container.DataItem,"id") %>' CommandName="pre" />
    </div></ItemTemplate>
        <ItemStyle Width="200px" />
    </asp:TemplateField>
    </Columns>
        <PagerSettings FirstPageText="首页" LastPageText="末页" NextPageText="下一页" Position="TopAndBottom"
            PreviousPageText="上一页" Mode="NextPreviousFirstLast" PageButtonCount="5"  />
        <AlternatingRowStyle BackColor="White" />
        <HeaderStyle BackColor="#C0C0FF" />
    </asp:GridView>
   </div> 
    </ajax:AjaxPanel>
</form>
</body>
</html>aspx.cs
--------------------------------
protected void GVXuanshou_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        CXuanshou xuanshou = new CXuanshou();
        if (e.CommandName == "delete")
        {
            xuanshou.DeleteXuanshou(int.Parse(e.CommandArgument.ToString()));
            InitGrid();
        }
        if (e.CommandName == "mdf")        {
            SqlDataReader recu = xuanshou.GetSingleXuanshou(int.Parse(e.CommandArgument.ToString()));
            if (recu.Read())
            {
                txtMdfAge.Text = recu["age"].ToString();
                txtMdfName.Text = recu["name"].ToString();
                txtMdfGuoji.Text = recu["guoji"].ToString();
                MdfContent.Value = recu["content"].ToString();
                string sex = recu["sex"].ToString();
                id.Value = recu["id"].ToString();
                recu.Close();
                if (sex == "男")
                {
                    RBMdfMan.Checked = true;
                }
                else
                {
                    RBMdfWoman.Checked = true;
                }
                AjaxCallHelper.Write("ShowMdfDialog();");
            }
            else
            {
                recu.Close();
                AjaxCallHelper.WriteAlert("选手信息已不存在，请重新操作!");
                InitGrid();
            }
        }
        if (e.CommandName == "pre")
        {
            
        }
    }