变量名不能在此范围内声明

本文关键字：范围内 声明 不能 变量名 | 更新日期: 2023-09-27 18:06:21

我想到目前为止我已经一切正常了。如果本地变量"req"错误，则会留下一个错误…它已经在System.Net.WebRequest上面声明过了req = null;但我试图清除它之前使用WebRequest req = WebRequest. create…我不需要这么做吗?

while (listId.Items.Count > 0)
            {
                // making the first item as selected.
                listId.SelectedIndex = 0;
                foreach (object o in listProxy.Items)
                {
                    string strProxy = o as string;
                    WebProxy proxyObject = new WebProxy(strProxy, true); // insert listProxy proxy here
                    WebRequest.DefaultWebProxy = proxyObject;
                    string strURL = "http://www.zzzz.com"; // link from listId and insert here
                    System.Net.WebRequest req = null;
                    try
                    {
                        WebRequest req = WebRequest.Create(strURL + "/book.php?qid=" + listId.SelectedItem as string);
                        req.Proxy = proxyObject;
                        req.Method = "POST";
                        req.Timeout = 5000;
                    }
                    catch (Exception eq)
                    {
                        string sErr = "Cannot connect to " + strURL + " : " + eq.Message;
                        MessageBox.Show(sErr, strURL, MessageBoxButtons.OK, MessageBoxIcon.Stop);
                    }
                }
                // remove the selected item.
                listId.Items.RemoveAt(0);
                // refreshing the list.
                listId.Refresh();
            }

变量名不能在此范围内声明

您已经在外部作用域中声明了它，因此您不能在内部作用域中重新声明它。不需要重新申报WebRequest。删除两个声明中的一个。我将删除外部作用域中的那个，因为看起来您不需要在try块之外引用它。

while (listId.Items.Count > 0)
{
    // making the first item as selected.
    listId.SelectedIndex = 0;
    foreach (object o in listProxy.Items)
    {
        string strProxy = o as string;
        WebProxy proxyObject = new WebProxy(strProxy, true); // insert listProxy proxy here
        WebRequest.DefaultWebProxy = proxyObject;
        string strURL = "http://www.zzzz.com"; // link from listId and insert here
        try
        {
            WebRequest req = WebRequest.Create(strURL + "/book.php?qid=" + listId.SelectedItem as string);
            req.Proxy = proxyObject;
            req.Method = "POST";
            req.Timeout = 5000;
        }
        catch (Exception eq)
        {
            string sErr = "Cannot connect to " + strURL + " : " + eq.Message;
            MessageBox.Show(sErr, strURL, MessageBoxButtons.OK, MessageBoxIcon.Stop);
        }
    }
    // remove the selected item.
    listId.Items.RemoveAt(0);
    // refreshing the list.
    listId.Refresh();
}

变化:

WebRequest req = WebRequest.Create(strURL + "/book.php?qid=" + listId.SelectedItem as string);

: 

   req = WebRequest.Create(strURL + "/book.php?qid=" + listId.SelectedItem as string);

您不能在同一作用域中声明两个具有相同名称的局部变量，因此不使用WebRequest req = WebRequest.Create(....)而使用req = WebRequest.Create(...)

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