问Asp.net，Xml错误

EN

**AdminWelcomeMsg.aspx**
<%@ Page Language="C#" MasterPageFile="ContentMasterPage.master" Debug="true"%>

<%@ Import Namespace="System.Xml"%>
<%@ Import Namespace="System.Xml.Xsl" %>
<%@ Import Namespace="System.Xml.XPath" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.IO" %>

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
<script runat="server">
    void Page_load(object sender, System.EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            WelcomeData.DataSource = LoadWelcome();
            WelcomeData.DataBind();
        }

        if (Session["error_msg"] != null)
        {
            ErrorMessage.Text = Session["error_msg"].ToString();
            Session["error_msg"] = null;
            ErrorMessage.Visible = true;
        }
    }


    protected DataSet LoadWelcome()
    {
        string sourceXML = Server.MapPath("../App_Data/DefaultMsg.xml");

        if ((!File.Exists(sourceXML)))
        {
            return null;
        }

        DataSet cachedDataSet = (DataSet)Session["MyWelcome"];

        if (((cachedDataSet != null)))
        {
            return cachedDataSet;
        }

        DataSet dataSet = new DataSet();

        try
        {
            dataSet.ReadXml(sourceXML);
            Session["MyWelcome"] = dataSet;
        }
        catch (Exception e)
        {
            ErrorMessage.Text = e.Message;
            dataSet = null;
        }

        return dataSet;
    }

    public void Welcome_Edit(object Sender, DataGridCommandEventArgs E)
    {
        WelcomeData.EditItemIndex = (int)E.Item.ItemIndex;
        WelcomeData.DataSource = LoadWelcome();
        WelcomeData.DataBind();
    }

    public void Welcome_Update(object Sender, DataGridCommandEventArgs E)
    {
        DataSet dataSet = LoadWelcome();
        int row = (int)E.Item.ItemIndex;
        TextBox EditText;
        EditText = (TextBox)E.Item.FindControl("txtpara");
        dataSet.Tables[0].Rows[row]["para"] = EditText.Text;

        dataSet.WriteXml(Server.MapPath("../App_Data/DefaultMsg.xml"));
        Session["MyWelcome"] = null;
        WelcomeData.EditItemIndex = -1;
        WelcomeData.DataSource = LoadWelcome();
        WelcomeData.DataBind();

        Session["error_msg"] = "The message was updated successfully";
        Response.Redirect("AdminWelcomeMsg.aspx");
    }

    public void Welcome_Cancel(object Sender, DataGridCommandEventArgs E)
    {
        WelcomeData.EditItemIndex = -1;
        Session["MyImage"] = null;
        WelcomeData.DataSource = LoadWelcome();
        WelcomeData.DataBind();
    }

    public void Welcome_Delete(object Sender, DataGridCommandEventArgs E)
    {
        DataSet dataSet = LoadWelcome();
        int row = (int)E.Item.ItemIndex;
        dataSet.Tables[0].Rows[row].Delete();
        dataSet.WriteXml(Server.MapPath("../App_Data/DefaultMsg.xml"));
        Session["MyWelcome"] = null;
        WelcomeData.EditItemIndex = -1;
        WelcomeData.DataSource = LoadWelcome();
        WelcomeData.DataBind();

        Session["error_msg"] = "The message was deleted successfully";
        Response.Redirect("AdminWelcomeMsg.aspx");
    }

    public void Welcome_Add(object Sender, EventArgs E)
    {
        DataSet dataSet = LoadWelcome();
        DataRow newRow;
        newRow = dataSet.Tables[0].NewRow();
        newRow["para"] = "";
        dataSet.Tables[0].Rows.Add(newRow);
        dataSet.WriteXml(Server.MapPath("../App_Data/DefaultMsg.xml"));
        Session["MyWelcome"] = null;
        WelcomeData.DataSource = LoadWelcome();
        WelcomeData.DataBind();
        WelcomeData.EditItemIndex = WelcomeData.Items.Count - 1;
        WelcomeData.DataSource = LoadWelcome();
        WelcomeData.DataBind();
    }

</script>
<div id="content">
    <div class="about">

<h2>Home Page Message</h2><hr />
        On this page you can add a message to the home page, update the 
        existing message or delete the message.<br /><br />
        <b><i><asp:Label ID="ErrorMessage" runat="server" ForeColor="Red" /></i></b><br /><br />
        <asp:LinkButton ID="LinkButton5" OnClick="Welcome_Add" Text="Add a welcome message" runat="server" /><br />

        <b><i><asp:Label ID="WelcomeMsg" runat="server" /></i></b><br />    

<asp:DataGrid ID="WelcomeData" AutoGenerateColumns="false" Width="100%" runat="server" 
 OnEditCommand="Welcome_Edit" OnUpdateCommand="Welcome_Update" OnCancelCommand="Welcome_Cancel" 
 OnDeleteCommand="Welcome_Delete">

<HeaderStyle ForeColor="White" BackColor="Maroon" Font-Bold="true" />
<ItemStyle BackColor="White" />
<AlternatingItemStyle BackColor="AntiqueWhite" />

<Columns>

<asp:TemplateColumn HeaderText="Welcome Msg">
    <ItemTemplate>
        <%# DataBinder.Eval(Container.DataItem, "para")%>
    </ItemTemplate>
    <EditItemTemplate>
        <asp:TextBox ID="txtpara" Size="25" Text='<%# DataBinder.Eval(Container.DataItem, "para")%>' runat="server"/>
        <asp:RequiredFieldValidator ID="RequiredFieldValidator1" ControlToValidate="txtpara" Font-Italic="true"
         Display="Dynamic" runat="server" ErrorMessage="(Required)" ForeColor="Red" ValidationGroup="Paras" />
    </EditItemTemplate>
</asp:TemplateColumn>

<asp:TemplateColumn>
    <ItemTemplate>
        <asp:LinkButton ID="LinkButton1" CommandName="Edit" Text="Edit" runat="server" ValidationGroup="Paras" />
        <asp:LinkButton ID="LinkButton2" CommandName="Delete" Text="Delete" runat="server" />
    </ItemTemplate>
    <EditItemTemplate>
        <asp:LinkButton ID="LinkButton3" CommandName="Cancel" Text="Cancel" runat="server"/>
        <asp:LinkButton ID="LinkButton4" CommandName="Update" Text="Update" runat="server" ValidationGroup="Paras" />
    </EditItemTemplate>
</asp:TemplateColumn>


</Columns>

</asp:DataGrid>


   </div>
        <img src="../App_Themes/theme/html/images/phone.jpg" alt="" width="953" height="87" /><br />
    </div>
</asp:Content>




**DefaultMsg.xml**
<?xml version="1.0" standalone="yes"?>
<welcome>
  <para>
    text text text
  </para>
  <para>
   text text text
 </para>
  <para>
    text text text
  </para>
  <para>
    text text text
  </para>
</welcome>