即使在asp.net中页面加载后如何保留全局字符串变量的值
我在保留我在独家新闻顶部定义的字符串变量时遇到问题，每次页面加载时字符串值都会变为空。下面是代码片段：
public partial class Caravan_For_Sale : System.Web.UI.Page
{
string check;
PagedDataSource pds = new PagedDataSource(); //paging
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
BindGrid();
}
}
private void BindGrid()
{
DataTable dt = null;
switch (check)
{
case "0-1500":
break;
case "1500-2000":
dt = caravans.GetFilterbyPrice1();
break;
case "2000+":
break;
default:
dt = caravans.GetAllCaravans();
break;
}
// DataTable dt = caravans.GetAllCaravans();
pds.DataSource = dt.DefaultView;
pds.AllowPaging = true;
pds.PageSize = 3;//add the page index when item exceeds 12 //Convert.ToInt16(ddlPageSize.SelectedValue);
pds.CurrentPageIndex = CurrentPage;
DataList1.RepeatColumns = 3; // 4 items per line
DataList1.RepeatDirection = RepeatDirection.Horizontal;
DataList1.DataSource = pds;
DataList1.DataBind();
lnkbtnNext.Enabled = !pds.IsLastPage;
lnkbtnPrevious.Enabled = !pds.IsFirstPage;
doPaging();
}
protected void lnkPrice2_Click(object sender, EventArgs e)
{
LinkButton _sender = (LinkButton)sender;
check = _sender.CommandArgument;
// items["test"] = test;
DataTable dt = caravans.GetFilterbyPrice2();
if (dt.Rows.Count < 3)
{
lnkbtnNext.Enabled = false;
lnkbtnPrevious.Enabled = false;
}
CurrentPage = 0;
BindGrid();
}
protected void dlPaging_ItemCommand(object source, DataListCommandEventArgs e)
{
if (e.CommandName.Equals("lnkbtnPaging"))
{
CurrentPage = Convert.ToInt16(e.CommandArgument.ToString());
BindGrid();
}
}
每次当 dlPaging_ItemCommand 变为活动状态（页面加载）时，字符串检查都会变为空。任何帮助或建议将不胜感激
I am having problems in retaining the string variable which I defined on the top of my scoop, everytime when page loads the string value becomes null. below is the snippet of the code:
public partial class Caravan_For_Sale : System.Web.UI.Page
{
string check;
PagedDataSource pds = new PagedDataSource(); //paging
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
BindGrid();
}
}
private void BindGrid()
{
DataTable dt = null;
switch (check)
{
case "0-1500":
break;
case "1500-2000":
dt = caravans.GetFilterbyPrice1();
break;
case "2000+":
break;
default:
dt = caravans.GetAllCaravans();
break;
}
// DataTable dt = caravans.GetAllCaravans();
pds.DataSource = dt.DefaultView;
pds.AllowPaging = true;
pds.PageSize = 3;//add the page index when item exceeds 12 //Convert.ToInt16(ddlPageSize.SelectedValue);
pds.CurrentPageIndex = CurrentPage;
DataList1.RepeatColumns = 3; // 4 items per line
DataList1.RepeatDirection = RepeatDirection.Horizontal;
DataList1.DataSource = pds;
DataList1.DataBind();
lnkbtnNext.Enabled = !pds.IsLastPage;
lnkbtnPrevious.Enabled = !pds.IsFirstPage;
doPaging();
}
protected void lnkPrice2_Click(object sender, EventArgs e)
{
LinkButton _sender = (LinkButton)sender;
check = _sender.CommandArgument;
// items["test"] = test;
DataTable dt = caravans.GetFilterbyPrice2();
if (dt.Rows.Count < 3)
{
lnkbtnNext.Enabled = false;
lnkbtnPrevious.Enabled = false;
}
CurrentPage = 0;
BindGrid();
}
protected void dlPaging_ItemCommand(object source, DataListCommandEventArgs e)
{
if (e.CommandName.Equals("lnkbtnPaging"))
{
CurrentPage = Convert.ToInt16(e.CommandArgument.ToString());
BindGrid();
}
}
The string check becomes null everytime when the dlPaging_ItemCommand becomes active(page loads). Any help or suggestions will be appreciated
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评论（3）
据我所知，您有两个选择：
1）再次加载。
不确定你的情况是否可行。这通常在处理数据库查询时完成。
2）将其放入 ViewState 中，如下所示：
然后加载它：
As far as I know, you have two options:
1) Load it again.
Not sure if it's possible in your case. This is usually done when dealing with database queries.
2) Put it in the ViewState just like this:
And load it after with this:
您的类会在每次加载时实例化，因此它不会在页面视图之间具有全局变量。您需要以某种方式存储它。就像在查询字符串或会话中一样。您还可以使用视图状态。
例如
ViewState("Variable") = "你的字符串"
Your class is instantiated on every load so it will not have a global variable from page view to page view. You will need to store it somehow. Like in the querystring or a session. You can also use the viewstate.
For example
ViewState("Variable") = "Your string"
正如其他人已经回答的那样，Viewstate 是要走的路。无论你做什么，请不要把它塞进会话中。
Viewstate is the way to go, as the other people have answered. Whatever you do, please don't stuff it in the session.