使用 PostBack 解决动态控件问题

• 下载 CreatDynamicControls.zip - 10.8 KB

引言

当我尝试在GridView中创建动态控件（例如标签、文本框、复选框等）时，页面回发后会丢失这些控件。我在网上搜索解决方案时没有找到任何相关信息，所以我决定自己解决这个问题。

问题定义

1. 首先，我在GridView中添加TemplateColumn
2. 然后，我在(ItemTemplate)中放置PlaceHolder控件

<asp:GridView ID="GridView1" runat="server" DataSourceID="ObjectDataSource1" 
    AutoGenerateColumns="False" OnRowDataBound="GridView1_RowDataBound" 
    OnDataBinding="GridView1_DataBinding" OnDataBound="GridView1_DataBound">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Bind("RoomID") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField>
<ItemTemplate>
<asp:PlaceHolder ID="PlaceHolder1" runat="server" 
    OnPreRender="PlaceHolder1_PreRender"></asp:PlaceHolder>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>

然后，在RowDataBound事件中，根据数据库字段（RoomID）创建控件的代码如下

protected void GridView1_RowDataBound(object sender,GridViewRowEventArgs e) { 
PlaceHolder plc = (PlaceHolder)e.Row.Cells[1].FindControl("PlaceHolder1"); 
Label lbl_RoomID = (Label)e.Row.Cells[0].FindControl("Label1"); 
Label lblinsert = new Label();
        CheckBox chk = new CheckBox();
        TextBox txt = new TextBox();
        chk.Text = "tttttttt";
        lblinsert.Text = "xxxxxxxxx";
        
        if (lbl != null)
        {
            switch(lbl.Text)
            {
                case "1":plc.Controls.Add(lblinsert);
                        arr.Add(lblinsert);break;
                case "2":plc.Controls.Add(chk);
                        arr.Add(chk);break;
                case "3": plc.Controls.Add(txt);
                        arr.Add(txt); break;
                default: lblinsert.Text = " Dummy ";
                        plc.Controls.Add(lblinsert);
                        arr.Add(lblinsert); break;
               
            }
        }
} 
}

解决方案

当我在RowDataBound事件中创建控件时，我将它们添加到ArrayList中，然后在DataBound事件中将ArrayList放入Session中

protected void GridView1_DataBound(object sender, EventArgs e)
{
Session.Add("arrcon", arr);
}

然后在PlaceHolder_PreRender事件中，我获取ArrayList并在其中重新创建控件，并带上其数据

Int count = 0 ;
protected void PlaceHolder1_PreRender(object sender, EventArgs e)
    {
        if (Page.IsPostBack)
        {
            arr = (ArrayList)Session["arrcon"];
            if (arr != null)
            {

                if (arr[count] is TextBox)
                {
                    TextBox txt = (TextBox)arr[count];
                    txt.Text = Request.Form[txt.UniqueID].ToString();
                    ((PlaceHolder)this.GridView1.Rows[count].Cells[1].FindControl(
                        "PlaceHolder1")).Controls.Add(txt);
                }
                else if (arr[count] is Label)
                {                
                    ((PlaceHolder)this.GridView1.Rows[count].Cells[1].FindControl(
                        "PlaceHolder1")).Controls.Add((Control)arr[count]);

                }
                else if (arr[count] is CheckBox)
                {
                    CheckBox chk = (CheckBox)arr[count];
                    if (Request.Form[chk.UniqueID] != null)
                    {
                        chk.Checked = true;
                    }
                    else
                    {
                        chk.Checked = false;
                    }
                    ((PlaceHolder)this.GridView1.Rows[count].Cells[1].FindControl(
                        "PlaceHolder1")).Controls.Add(chk);
                }
               count++;
            }
        }
    }

这样就解决了我的问题