WebForm FindControl的使用方法

Control.FindControl (String)：在当前的命名容器中搜索带指定 id参数的服务器控件。

有点类似javascript中的getElementById(string);

简单的例子：

 <form id="form1" runat="server">

     <div>

         <asp:TextBox ID="TextBox1" runat="server">TextBox</asp:TextBox>

         <asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />

         <br />

         <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>

      </div>

 </form>

如果需要获得页面中的"TextBox1",代码中可以使用this.TextBox1来引用，这里我们使用FindControl:

 protected void Button1_Click(object sender, EventArgs e)

   {

       //Control c = this.FindControl("TextBox1");

       //TextBox tb= (TextBox)c;

       //FindControl返回的是一个Control类型的控件，需要强制类型转化成TextBox类型

       TextBox tb=(TextBox)this.FindControl("TextBox1");

       this.Label1.Text = tb.Text;
    }

当TextBox1放到其他控件里应该怎么查找呢？

<div>

        <asp:Panel ID="Panel1" runat="server" Height="50px" ;125px">

           <asp:TextBox ID="TextBox1" runat="server">TextBox</asp:TextBox>

           <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>

           <asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />

        </asp:Panel>

    </div>

当TextBox1放到Panel里，似乎没什么影响 TextBox tb=(TextBox)this.FindControl("TextBox1")，

当查看生存页面的HTML代码是发现，TextBox的ID并没有改变，所以可以获得TextBox1。

<div>

       <div id="Panel1" style="height:50px;;">

          <input name="TextBox1" type="text" value="TextBoxdsd" id="TextBox1" />

          <span id="Label1">TextBoxdsd</span>

          <input type="submit" name="Button1" value="Button" id="Button1" />

        </div>

</div>

当TextBox1放到DataGrid中

 <asp:DataGrid ID="dg1" runat="server" OnSelectedIndexChanged="dg1_SelectedIndexChanged">

        <Columns>

           <asp:TemplateColumn>

              <ItemTemplate>

                 <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

              </ItemTemplate>

            </asp:TemplateColumn>

          <asp:ButtonColumn CommandName="Select" Text="选择"></asp:ButtonColumn>

        </Columns>

   </asp:DataGrid>

这时候this.FindControl("TextBox1")==null,无法获得TextBox1,查看生成页面HTML发现，页面有多个

<input name="dg1$ctl02$TextBox1" type="text" id="dg1_ctl02_TextBox1" />

<input name="dg1$ctl03$TextBox1" type="text" id="dg1_ctl03_TextBox1" />

TextBox1隐藏了，给DataGrid添加选择列，通过以下方法获得被选择行的TextBox1

protected void dg1_SelectedIndexChanged(object sender, EventArgs e)

  {

        Control c = this.dg1.Items[this.dg1.SelectedIndex].FindControl("TextBox1");

        //Control c = this.dg1.SelectedItem.FindControl("TextBox1");

        TextBox tb = (TextBox)c;

        tb.Text = "TextBox";

    }

 protected void dg1_EditCommand(object source, DataGridCommandEventArgs e)

  {

        TextBox tb = (TextBox)e.Item.FindControl("TextBox1");

        this.Label1.Text = tb.Text.ToString();

  }

如果是在DataGrid的页眉和页脚：

 ((TextBox)].Controls[].FindControl("TextBoxH")).Text = "Head";

 ((TextBox)].Controls[].Controls.Count -].FindControl("TextBoxF")).Text = "Footer";

TextBox1在Repeater中

   <asp:Repeater ID="Repeater1" runat="server" DataSourceID="SqlDataSource1" OnItemCommand="Repeater1_ItemCommand">

          <ItemTemplate>

            <asp:TextBox ID="TextBox1" runat="server" Text=""></asp:TextBox><%#DataBinder.Eval(Container.DataItem,"ProductName")%>

            <asp:Button ID="btn"OnClick="btn_click" runat="server" Text="dddd" /><br />

          </ItemTemplate>

   </asp:Repeater>

通过按钮来获得TextBox1:

   <asp:Repeater ID="Repeater1" runat="server" DataSourceID="SqlDataSource1" OnItemCommand="Repeater1_ItemCommand">

          <ItemTemplate>

            <asp:TextBox ID="TextBox1" runat="server" Text=""></asp:TextBox><%#DataBinder.Eval(Container.DataItem,"ProductName")%>

            <asp:Button ID="btn"OnClick="btn_click" runat="server" Text="dddd" /><br />

          </ItemTemplate>

   </asp:Repeater>

或者

foreach (RepeaterItem item in this.Repeater1.Items)

 {

       ((TextBox)item.FindControl("TextBox1")).Text = "Text2";

  }

自定义控件里的TextBox1

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="WebUserControl.ascx.cs" Inherits="WebUserControl" %>

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

引用<uc1:WebUserControl ID="WebUserControl1" runat="server" />

获取TextBox1:

((TextBox)this.WebUserControl1.FindControl("TextBox1")).Text = "userc";

模板页访问页面TextBox1

        //模板页的TextBox1

        TextBox tbM = (TextBox)this.FindControl("TextBox1");

        //页面中的TextBox1

        TextBox tbC = (TextBox)this.FindControl("ContentPlaceHolder1").FindControl("TextBox1");

        tbC.Text = tbM.Text;

页面使用模板页的TextBox1

       //模板页的TextBox1

        TextBox tbM = (TextBox)Master.FindControl("TextBox1");

        //本页面的TextBox1

        //错误的方法：TextBox tbC = (TextBox)this.FindControl("TextBox1");

        TextBox tbC = (TextBox)Master.FindControl("ContentPlaceHolder1").FindControl("TextBox1");

        tbM.Text = tbC.Text.ToString();