回发后丢失数据的占位符
回发后丢失数据的占位符
提问于 2018-06-08 00:38:29
我正在将数据库表中的id号列表读取到占位符文本框中，但是，如果我这样做，单击一个按钮，数据就会被删除。
protected void btnSearch_Click(object sender, EventArgs e)
{
while (myReader.Read())
{
TextBox txt = new TextBox();
txt.Text = (string)myReader["idNumber"];
txt.ID = "txt" + i;
txt.ReadOnly = true;
ContentPlaceHolder1.Controls.Add(txt);
ContentPlaceHolder1.Controls.Add(new LiteralControl(" "));
i++;
}
}回答 1
Stack Overflow用户
回答已采纳
发布于 2018-06-08 01:20:38
在web窗体中使用动态添加的控件时，这是一个常见的问题(特别是如果您来自winforms背景)。ASP.NET网页窗体中的页是无状态的，并在每次回发时重新构造。因此，如果在服务器事件期间将控件添加到页面，如果希望它出现，则还必须在后续页面加载时将其添加到页面。您可以使用类似于以下内容的内容来完成此操作：
protected List<Control> ControlCache
{
get => (List<Control>)(Session["cachedControlsForPageX"] = (Session["cachedControlsForPageX"] as List<Control>) ?? new List<Control>());
set => Session["cachedControlsForPageX"] = value;
}
/* If you can't use C# 7's expression bodied property accessors, here's the equivalent in blocks:
protected List<Control> ControlCache
{
get { return (List<Control>)(Session["cachedControlsForPageX"] = (Session["cachedControlsForPageX"] as List<Control>) ?? new List<Control>()); }
set { Session["cachedControlsForPageX"] = value; }
}
*/
protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack)
{
foreach (var control in ControlCache)
{
ContentPlaceHolder1.Controls.Add(control);
ContentPlaceHolder1.Controls.Add(new LiteralControl(" "));
}
}
else
ControlCache = null;
}
protected void btnSearch_Click(object sender, EventArgs e)
{
while (myReader.Read())
{
TextBox txt = new TextBox();
txt.Text = (string)myReader["idNumber"];
txt.ID = "txt" + i;
txt.ReadOnly = true;
ContentPlaceHolder1.Controls.Add(txt);
ContentPlaceHolder1.Controls.Add(new LiteralControl(" "));
ControlCache.Add(txt);
i++;
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/50746291
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