在HTML标记中声明asp.net控件

Question

是否可以写这样的东西？

    <input class="form-control" id="name" name="name"
     placeholder='<asp:Label runat="server" ID="lblFormName"></asp:Label>' type="text" required autofocus />

Answer 1

您想为HTML元素的某个属性分配一些值吗？

<asp:HiddenField runat="server" ID="lblFormName" />
<input class="form-control" id="name" name="name" placeholder='<%# lblFormName.Value %>' ...

然后从CodeBehind传递lblFormName.Value。

Answer 2

您无法在纯HTML页面中声明单个ASP.NET控件。它必须是由服务器处理的ASP.NET页面（aspx）。

Answer 3

解决方案1：让ASP.Net渲染额外的属性

您可以使用本机TextBox控件：

<asp:TextBox runat="server"
             ID="name" 
             required="required" 
             autofocus="autofocus" 
             CssClass="form-control" 
             placeholder="myplaceholder" />

额外属性（不属于TextBox类的属性）将按原样呈现：

Html结果：

<input name="ctl00$MainContent$name" 
       type="text"  
       id="MainContent_name"  
       class="form-control"  
       required="required"  
       autofocus="autofocus"  
       placeholder="myplaceholder" />

如果生成的ID必须是显式的，您可以添加CliendIDMode="Static"：

<asp:TextBox runat="server" 
             ID="name" 
             required="required" 
             autofocus="autofocus" 
             CssClass="form-control" 
             placeholder="myplaceholder" 
             ClientIDMode="Static" />

结果：

<input name="ctl00$MainContent$name"  
       type="text"  
       id="name"  
       class="form-control"  
       required="required"  
       autofocus="autofocus"  
       placeholder="myplaceholder" />

解决方案2：编写自己的控件

更好的方法是扩展文本框类：

using System.Web.UI.WebControls;

namespace WebApplication1.Controls
{
    public class TextBoxEx : TextBox
    {

        protected override void AddAttributesToRender(System.Web.UI.HtmlTextWriter writer)
        {
            if (AutoFocus) writer.AddAttribute("autofocus", "autofocus");
            if (Required) writer.AddAttribute("required", "required");
            if (!string.IsNullOrEmpty(PlaceHolder)) writer.AddAttribute("placeholder", PlaceHolder);

            base.AddAttributesToRender(writer);
        }

        public string PlaceHolder
        {
            get  {
                var obj = ViewState["PlaceHolder"];
                return obj != null ? (string)obj : default(string);
            }
            set { ViewState["PlaceHolder"] = value; }
        }

        public bool AutoFocus
        {
            get {
                var obj = ViewState["AutoFocus"];
                return obj != null ? (bool)obj : default(bool);
            }
            set { ViewState["AutoFocus"] = value; }
        }

        public bool Required
        {
            get {
                var obj = ViewState["Required"];
                return obj != null ? (bool)obj : default(bool);
            }
            set { ViewState["Required"] = value; }
        }
    }
}

然后您可以注册并使用控件：

<%@ Register Assembly="WebApplication1" TagPrefix="local" Namespace="WebApplication1.Controls" %>

....

<local:TextBoxEx runat="server" required="true" autofocus="true" PlaceHolder="my placeholder" />