📄 给静态datagrid动态添加列的问题.txt
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如果动态添加了列的话，需要在下一次PostBack时，在LoadViewState或更早把这些列重新添加。原因是，在Page类递归调用LoadViewState时，会调用DataGrid的CreateChildControls，而DataGrid的(实际上是它的父类的实现)CreateChildControls会调用DataGrid的CreateControlHierarchy()方法。在其中，DataGrid会根据当前的列的数目构造DataGridItem里的东西，然后从ViewState里恢复原来的数据。如果你没有重新添加你的动态列的话，你的动态列在PostBack后就会消失，更不用谈触发列里的控件的事件了
检验你的动态控件在PostBack后是否还在的一个方法是，加一个按钮看PostBack后的行为
1.WebForm1.aspx
<%@ Page language="c#" Codebehind="WebForm1.aspx.cs" AutoEventWireup="false" Inherits="WebTest1.WebForm1" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<body>
<form runat="server" ID="Form1">
<asp:DataGrid id="DataGrid1" runat="server" GridLines="Both" AutoGenerateColumns="false">
<Columns>
<asp:ButtonColumn HeaderText="Static Button" Text="Click Me" CommandName="Static" />
<asp:TemplateColumn HeaderText="Data">
<ItemTemplate>
<%#Container.DataItem%>
</ItemTemplate>
</asp:TemplateColumn>
</Columns>
</asp:DataGrid>
<asp:Button id="btnAddAColumn" runat="server" Text="Add a column" />
<asp:Button id="btnRefresh" runat="server" Text="Refresh" />
</form>
</body>
</HTML>
2.WebForm1.aspx.cs
using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
namespace WebTest1
{
/// <summary>
/// WebForm1 的摘要说明。
/// </summary>
public class WebForm1 : System.Web.UI.Page
{
protected System.Web.UI.WebControls.DataGrid DataGrid1;
protected System.Web.UI.WebControls.Button btnAddAColumn;
protected System.Web.UI.WebControls.Button btnRefresh;
private void Page_Load(object sender, System.EventArgs e)
{
if (!IsPostBack)
{
BindGrid();
}
}
void BindGrid()
{
DataGrid1.DataSource = new string[] {"a","b","c"};
DataGrid1.DataBind();
}
#region Web 窗体设计器生成的代码
override protected void OnInit(EventArgs e)
{
//
// CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
//
InitializeComponent();
base.OnInit(e);
}
/// <summary>
/// 设计器支持所需的方法 - 不要使用代码编辑器修改
/// 此方法的内容。
/// </summary>
private void InitializeComponent()
{
this.DataGrid1.ItemCommand += new System.Web.UI.WebControls.DataGridCommandEventHandler(this.DataGrid1_ItemCommand);
this.btnAddAColumn.Click += new System.EventHandler(this.btnAddAColumn_Click);
this.Load += new System.EventHandler(this.Page_Load);
}
#endregion
private void DataGrid1_ItemCommand(object source, System.Web.UI.WebControls.DataGridCommandEventArgs e)
{
Response.Write("ItemCommand is called<BR>");
LinkButton btn = e.CommandSource as LinkButton;
if (btn != null)
Response.Write(String.Format("{0} is clicked on row {1}", btn.CommandName, e.Item.ItemIndex));
}
public void CreateGridColumn(DataGrid OperationDataGrid)
{
ButtonColumn NewButCol = new ButtonColumn() ;
NewButCol.Text = "编辑" ;
NewButCol.HeaderText = "操作" ;
NewButCol.CommandName = "Edit" ;
NewButCol.ButtonType = ButtonColumnType.LinkButton;
NewButCol.Visible = true ;
OperationDataGrid.Columns.Add(NewButCol) ;
//OperationDataGrid.Columns.AddAt(1,NewButCol) ;
}
private void btnAddAColumn_Click(object sender, System.EventArgs e)
{
CreateGridColumn(DataGrid1);
ButtonAdded = true;
BindGrid();
btnAddAColumn.Visible = false;
}
bool ButtonAdded
{
get
{
object o = ViewState["ButtonAdded"];
if (o == null)
return false;
else return (bool)o;
}
set { ViewState["ButtonAdded"] = value;}
}
//重要
protected override void LoadViewState(object savedState)
{
base.LoadViewState(savedState);
//在这里重新添加，假如已经添加的话
if (ButtonAdded)
CreateGridColumn(DataGrid1);
}
}
}
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