Asp.net动态生成页面控件的办法

在Asp.net开发中，有时需要在页面中动态添加控件。这些控件可以是普通的html标签，也可以是Asp.net独有的服务器端控件。关于动态写入html标签控件，大家都熟悉，这里就不再表述。本文讨论的重点是：如何动态写入服务器端控件，并且在页面PostBack到Server端时，在Server端来获取被动态写入的服务器端控件的各种属性。下面为一个实例：

需求：
1. 用户在UI上输入一个数值(比如：5)，系统动态为用户加载这个数值的Url Address输入域;
2. 用户输入的Url Address内容需要通过Url格式验证;
3. 用户提交输入内容后，系统给出提交的结果

最终效果：

设计过程：

1. Css样式设置：
  <style type="text/css">

        .item
        {
        margin:10px;
        border-bottom:solid 1px #CCC;
        }

        .item2
        {
        margin:5px;
        }

        .input
        {
        width:200px;
        }
</style>

2．前台页面代码：
        <div>
            <div class="item">
                Please input a number:
                <asp:TextBox runat="server" CssClass="item" ID="txtTextCount"></asp:TextBox>
                <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="txtTextCount" ValidationGroup="CreateTextBox" Display="Dynamic"
                    ErrorMessage="Required to input content!"></asp:RequiredFieldValidator>
                <asp:RegularExpressionValidator ID="RegularExpressionValidator1" ControlToValidate="txtTextCount" ValidationGroup="CreateTextBox" Display="Dynamic"
                    runat="server" ErrorMessage="Only number is valid!" ValidationExpression="^\d+$"></asp:RegularExpressionValidator>  
                <asp:Button runat="server" ID="btnCreate" Text="Create TextBox List" ValidationGroup="CreateTextBox"
                    onclick="btnCreate_Click" />  
                <asp:Button runat="server" ID="btnOK" Text="Get TextBox Content" ValidationGroup="ShowListContent"
                    onclick="btnOK_Click" />
            </div>
            <div runat="server" id="divControls" class="item"></div>
            <div runat="server" id="divMessage">
            </div>
        </div>

2．前台页面代码

       <div>

            <div class="item">
                Please input a number:
                <asp:TextBox runat="server" CssClass="item" ID="txtTextCount"></asp:TextBox>
                <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="txtTextCount" ValidationGroup="CreateTextBox" Display="Dynamic"
                    ErrorMessage="Required to input content!"></asp:RequiredFieldValidator>
                <asp:RegularExpressionValidator ID="RegularExpressionValidator1" ControlToValidate="txtTextCount" ValidationGroup="CreateTextBox" Display="Dynamic"
                    runat="server" ErrorMessage="Only number is valid!" ValidationExpression="^\d+$"></asp:RegularExpressionValidator>  
                <asp:Button runat="server" ID="btnCreate" Text="Create TextBox List" ValidationGroup="CreateTextBox"
                    onclick="btnCreate_Click" />  
                <asp:Button runat="server" ID="btnOK" Text="Get TextBox Content" ValidationGroup="ShowListContent"
                    onclick="btnOK_Click" />
            </div>
            <div runat="server" id="divControls" class="item"></div>
            <div runat="server" id="divMessage">
            </div>
        </div>

说明，动态创建的TextBox们将装载到divControls中。

3．后台代码：
       ///<summary>

        /// Create textbox list
        ///</summary>
        ///<param name="num">textbox list count</param>
        private void CreateTextBoxList(int num)
        {
            HtmlGenericControl div;
            HtmlGenericControl span;
            TextBox txt;
            RegularExpressionValidator rev;

            for (int i = 0; i < num; i++)
            {
                //创建div
                div = new HtmlGenericControl();
                div.TagName = "div";
                div.ID = "divTextBox" + i.ToString();
                div.Attributes["class"] = "item2";

                //创建span
                span = new HtmlGenericControl();
                span.ID = "spanTextBox" + i.ToString();
                span.InnerHtml = "Url Address" + (i+1).ToString() + ":";

                //创建TextBox
                txt = new TextBox();
                txt.ID = "txt" + i.ToString();
                txt.CssClass = "input";

                //创建格式验证控件，并且将其关联到对应的TextBox
                rev = new RegularExpressionValidator();
                rev.ID = "rev" + i.ToString();
                rev.ControlToValidate = txt.ID;
                rev.Display = ValidatorDisplay.Dynamic;
                rev.ValidationGroup = "ShowListContent";
                rev.ValidationExpression = @"(http(s)?://)?([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?";
                rev.ErrorMessage = "Invalid url Address!";

                //添加控件到容器
                div.Controls.Add(span);
                div.Controls.Add(txt);
                div.Controls.Add(rev);
                divControls.Controls.Add(div);
            }
        }

        protected void Page_Load(object sender, EventArgs e)
        {
            if (this.IsPostBack)
            {
                int txtCount = int.Parse(txtTextCount.Text);

                // 注意：每次PostBack时，都需要重新动态创建TextBox
                CreateTextBoxList(txtCount);
            }
        }

        protected void btnCreate_Click(object sender, EventArgs e)
        {
            txtTextCount.Enabled = false;
            btnCreate.Enabled = false;
        }

        protected void btnOK_Click(object sender, EventArgs e)
        {
            TextBox txt;
            StringBuilder sbResult = new StringBuilder() ;
            int txtCount = int.Parse(txtTextCount.Text);

            //遍历获取动态创建的TextBox们中的Text值
            for (int i = 0; i < txtCount; i++)
            {
                //注意：这里必须通过上层容器来获取动态创建的TextBox，才能获取取ViewState内容
                txt = divControls.FindControl("txt" + i.ToString()) as TextBox;

                if (txt != null && txt.Text.Trim().Length > 0)
                {
                    sbResult.AppendFormat("Url Address{0}: {1}.<br />", i+1, txt.Text.Trim());
                }
            }

            divMessage.InnerHtml = sbResult.ToString();
        }