C# 页面范围变量消失
假设我有以下asp.net页面:C# 页面范围变量消失,c#,asp.net,.net,C#,Asp.net,.net,假设我有以下asp.net页面: public partial class SamplePage : System.Web.UI.Page { private int UserID; protected void Page_Load(object sender, EventArgs e) { } protected void btnSearchUser_Click(object sender, EventArgs e) { Use
public partial class SamplePage : System.Web.UI.Page
{
private int UserID;
protected void Page_Load(object sender, EventArgs e)
{
}
protected void btnSearchUser_Click(object sender, EventArgs e)
{
UserID = 5;
}
protected void btnSubmit_Click(object sender, EventArgs e)
{
Response.Write(UserID.ToString());
}
}
但是UserID总是0。如何使其始终为5?因为按钮的点击会导致回发,并且由于HTTP协议是无状态的,因此回发过程中数据总是丢失。。因此,您必须将该用户标识存储到viewstate中以维护其值…这就是为什么我们在Asp.net中使用状态管理的概念。 然而,你可以做到这一点
public partial class SamplePage : System.Web.UI.Page
{
int UserID;
protected void Page_Load(object sender, EventArgs e)
{
}
protected void btnSearchUser_Click(object sender, EventArgs e)
{
UserID=5;
ViewState["UserID"] = UserID;
}
protected void btnSubmit_Click(object sender, EventArgs e)
{
if(ViewState["UserID"]!=null)
Response.Write(ViewState["UserID"].ToString());
}
}
要在回发之间持久化数据,需要将其置于当前控件的视图状态:
private int UserID
{
get
{
return this.ViewState["UserID"] as int? ?? -1; // if data is missing, default value -1 will be returned
}
set
{
this.ViewState["UserID"] = value;
}
}