Question

我正在使用VS 2015，我的编码语言是C＃。我试图在aspx中创建一个简单的网站，产生服务器时间，并允许您更改时钟的颜色。无论如何，我有这个错误说＆＃34;名称timeLabel在当前上下文中不存在＆＃34;到目前为止，这是我的代码。

    <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebTime.aspx.cs" Inherits="Web.WebTime" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Server Time</title>
    <style type="text/css">
       .timeStyle {
          color: red;
          font-size: xx-large;
          background-color: blanchedalmond;
       }
    </style>
</head>
<body>
    <div> 
       <h2>
          Current time on the Web server:</h2>
       <p>
          <span id="timeLabel" runat="server" class="timeStyle" >02:55:28</span>
       </p>
           <p>
          New background color:
          <asp:DropDownList ID="backColorDropDownList" runat="server" AutoPostBack="True">
             <asp:ListItem>Black</asp:ListItem>
             <asp:ListItem>White</asp:ListItem>
             <asp:ListItem>Blue</asp:ListItem>
             <asp:ListItem>Red</asp:ListItem>
             <asp:ListItem>Green</asp:ListItem>
             <asp:ListItem>Purple</asp:ListItem>
             <asp:ListItem>Yellow</asp:ListItem>
          </asp:DropDownList>
       </p>
       <p>
          New foreground color:
          <asp:DropDownList ID="foreColorDropDownList" runat="server" AutoPostBack="True">
             <asp:ListItem>Yellow</asp:ListItem>
             <asp:ListItem>Black</asp:ListItem>
             <asp:ListItem>White</asp:ListItem>
             <asp:ListItem>Blue</asp:ListItem>
             <asp:ListItem>Red</asp:ListItem>
             <asp:ListItem>Green</asp:ListItem>
             <asp:ListItem>Purple</asp:ListItem>
          </asp:DropDownList>
       </p>
       <p>
          New font size:
          <asp:DropDownList ID="fontSizeDropDownList" runat="server" AutoPostBack="True">
             <asp:ListItem>24</asp:ListItem>
             <asp:ListItem>22</asp:ListItem>
             <asp:ListItem>20</asp:ListItem>
             <asp:ListItem>18</asp:ListItem>
             <asp:ListItem>16</asp:ListItem>
          </asp:DropDownList>
       </p>
    </div>
</body>
</html>

这也是我的CodeBehind文件：

// Code-behind file for a page that displays the current time
// and updates properties based on user input.
using System;
using System.Drawing;

namespace Web
{
    public partial class WebTime : System.Web.UI.Page
    {
        // initializes the contents of the page
        protected void Page_Init(object sender, EventArgs e)
        {
            // display the server's current time in timeLabel
            timeLabel.Text = DateTime.Now.ToString("hh:mm:ss");
        } // end method Page_Init

        // when loading due to a postback, Page_Load modifies 
        // the Label's properties based on user input
        protected void Page_Load(object sender, EventArgs e)
        {
            // if this is a postback, process user input
            if (IsPostBack)
            {
                // retrieve the values submitted by the user
                string backColor = backColorDropDownList.SelectedItem.Text;
                string foreColor = foreColorDropDownList.SelectedItem.Text;
                int fontSize =
                   Convert.ToInt32(fontSizeDropDownList.SelectedItem.Text);

                // modify timeLabel based on the user's selections
                timeLabel.BackColor = Color.FromName(backColor);
                timeLabel.ForeColor = Color.FromName(foreColor);
                timeLabel.Font.Size = fontSize;
            } // end if
        }  
    }       
}

错误发生在我的CodeBehind文件中。

＆＃34; timeLabel＆＃34;，＆＃34; backColorDropDownList＆＃34;，＆＃34; foreColorDropDownList＆＃34;，＆＃34; fontSizeDropDownList＆＃34;有错误。

任何帮助都会非常感激！

Answer 1

您应该将asp控件封装在表单元素中：

＆＃13;

...
<body>
  <form runat="server">
    <div> 
       <h2>
          Current time on the Web server:</h2>
       <p>
          <span id="timeLabel" runat="server" class="timeStyle" >02:55:28</span>
       </p>
           <p>
          New background color:
          <asp:DropDownList ID="backColorDropDownList" runat="server" AutoPostBack="True">
             <asp:ListItem>Black</asp:ListItem>
             <asp:ListItem>White</asp:ListItem>
             <asp:ListItem>Blue</asp:ListItem>
             <asp:ListItem>Red</asp:ListItem>
             <asp:ListItem>Green</asp:ListItem>
             <asp:ListItem>Purple</asp:ListItem>
             <asp:ListItem>Yellow</asp:ListItem>
          </asp:DropDownList>
       </p>
       <p>
          New foreground color:
          <asp:DropDownList ID="foreColorDropDownList" runat="server" AutoPostBack="True">
             <asp:ListItem>Yellow</asp:ListItem>
             <asp:ListItem>Black</asp:ListItem>
             <asp:ListItem>White</asp:ListItem>
             <asp:ListItem>Blue</asp:ListItem>
             <asp:ListItem>Red</asp:ListItem>
             <asp:ListItem>Green</asp:ListItem>
             <asp:ListItem>Purple</asp:ListItem>
          </asp:DropDownList>
       </p>
       <p>
          New font size:
          <asp:DropDownList ID="fontSizeDropDownList" runat="server" AutoPostBack="True">
             <asp:ListItem>24</asp:ListItem>
             <asp:ListItem>22</asp:ListItem>
             <asp:ListItem>20</asp:ListItem>
             <asp:ListItem>18</asp:ListItem>
             <asp:ListItem>16</asp:ListItem>
          </asp:DropDownList>
       </p>
    </div>

 </form>
</body>
...

＆＃13;

Answer 2

我不确定为什么你会在这么简单的事情上收到错误。只需粘贴以下代码即可显示当前时间并查看

for (int i = 0; ; i++) {
    int a[][]=new int[i][i];
    System.out.println(i + " " + Arrays.toString(a));
}

让我知道出现的错误消息

名称timeLabel在当前上下文中不存在

2 个答案: