DataGrid的状态问题！

用DataGrid动态生成列。当点击编辑后不能使用试图状态。需要将if(!this.IsPostBack)
SetField();//实现列的动态生成
改成
SetField();
才能解决。代码如下，肯求帮助！
<%@ Page language="c#" Codebehind="WebForm3.aspx.cs" AutoEventWireup="false" Inherits="aspnet0625.WebForm3" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm3</title>
<meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
<meta name="CODE_LANGUAGE" Content="C#">
<meta name="vs_defaultClientScript" content="JavaScript">
<meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5">
</HEAD>
<body>
<form runat="server" ID="Form1">
<FONT face="宋体">
<asp:DataGrid id="DataGrid1" runat="server"></asp:DataGrid></FONT>
</form>
</body>
</HTML>cs..
public class WebForm3 : System.Web.UI.Page
{
protected System.Web.UI.WebControls.DataGrid DataGrid1; private void Page_Load(object sender, System.EventArgs e)
{                                               this.DataGrid1.AutoGenerateColumns=false;
if(!this.IsPostBack)
SetField();
EditCommandColumn editcolum=new EditCommandColumn();
editcolum.EditText="edit";
editcolum.UpdateText="update";
editcolum.CancelText="cancel";
this.DataGrid1.Columns.Add(editcolum); SetBinded();
}

public void SetBinded()
{
                         DataXml data = new DataXml(); this.DataGrid1.DataSource=data.ReadData(Server.MapPath(".\\xml\\tbAPQ0001.xml"));//用DataTable做数据源
this.DataGrid1.DataBind();
} public void SetField()
{
BoundColumn colum1=new BoundColumn();
colum1.HeaderText="Property";
colum1.DataField="property";
this.DataGrid1.Columns.Add(colum1);
}
#region Web 窗体设计器生成的代码
private void InitializeComponent()
{    
this.DataGrid1.CancelCommand += new System.Web.UI.WebControls.DataGridCommandEventHandler(this.DataGrid1_CancelCommand);
this.DataGrid1.EditCommand += new System.Web.UI.WebControls.DataGridCommandEventHandler(this.DataGrid1_EditCommand);
this.DataGrid1.UpdateCommand += new System.Web.UI.WebControls.DataGridCommandEventHandler(this.DataGrid1_UpdateCommand);
} #endregion private void DataGrid1_EditCommand(object source, System.Web.UI.WebControls.DataGridCommandEventArgs e)
{
this.DataGrid1.EditItemIndex = e.Item.ItemIndex;
SetBinded();
} private void DataGrid1_CancelCommand(object source, System.Web.UI.WebControls.DataGridCommandEventArgs e)
{
this.DataGrid1.EditItemIndex = -1;
SetBinded();

} private void DataGrid1_UpdateCommand(object source, System.Web.UI.WebControls.DataGridCommandEventArgs e)
{
this.DataGrid1.EditItemIndex=-1;
SetBinded();
}
}