ASP.NET Tutorial/Sessions/ViewState
Содержание
Disable ViewState for a certain control
<source lang="csharp">
<%@ Page Language="VB" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <script runat="server">
Sub btnAdd_Click(ByVal sender As Object, ByVal e As EventArgs)
Label1.Text = (Int32.Parse(Label1.Text) + 1).ToString()
Label2.Text = (Int32.Parse(Label2.Text) + 1).ToString()
End Sub
</script> <html xmlns="http://www.w3.org/1999/xhtml" > <head id="Head1" runat="server">
<title>Disable View State</title>
</head> <body>
<form id="form1" runat="server">
Label 1:
<asp:Label
id="Label1"
EnableViewState="false"
Text="0"
Runat="server" />
Label 2:
<asp:Label
id="Label2"
Text="0"
Runat="server" />
<asp:Button
id="btnAdd"
Text="Add"
OnClick="btnAdd_Click"
Runat="server" />
</form>
</body> </html></source>
Insert view state data in Page render event (C#)
<source lang="csharp">
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!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>Untitled Page</title>
</head> <body>
<form id="form1" runat="server">
</form>
</body> </html> File: Default.aspx.cs using System; using System.Data; using System.Configuration; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; using System.IO; public partial class _Default : System.Web.UI.Page {
protected void Page_Load(object sender, EventArgs e)
{
ViewState["Example"] = "nfex.ru";
}
protected override void Render(System.Web.UI.HtmlTextWriter writer)
{
System.IO.StringWriter stringWriter = new System.IO.StringWriter();
HtmlTextWriter htmlWriter = new HtmlTextWriter(stringWriter);
base.Render(htmlWriter);
string html = stringWriter.ToString();
int StartPoint = html.IndexOf("<input type=\"hidden\" name=\"__viewstate\"");
if (StartPoint >= 0)
{
int EndPoint = html.IndexOf("/>", StartPoint) + 2;
string viewstateInput = html.Substring(StartPoint, EndPoint - StartPoint);
html = html.Remove(StartPoint, EndPoint - StartPoint);
int FormEndStart = html.IndexOf("</form>") - 1;
if (FormEndStart >= 0)
{
html = html.Insert(FormEndStart, viewstateInput);
}
}
writer.Write(html);
}
}</source>
Insert view state data in Page render event (VB)
<source lang="csharp">
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %> <!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>Untitled Page</title>
</head> <body>
<form id="form1" runat="server">
</form>
</body> </html> File: Default.aspx.vb Imports System.IO Partial Class _Default
Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
ViewState("Example") = "nfex"
End Sub
Protected Overrides Sub Render(ByVal writer As System.Web.UI.HtmlTextWriter)
Dim stringWriter As System.IO.StringWriter = New System.IO.StringWriter
Dim htmlWriter As HtmlTextWriter = New HtmlTextWriter(stringWriter)
MyBase.Render(htmlWriter)
Dim html As String = stringWriter.ToString
Dim StartPoint As Integer
StartPoint = html.IndexOf("<input type=\""hidden\"" name=\""__viewstate\""")
If (StartPoint >= 0) Then
Dim EndPoint As Integer = (html.IndexOf("/>", StartPoint) + 2)
Dim viewstateInput As String
viewstateInput = html.Substring(StartPoint, (EndPoint - StartPoint))
html = html.Remove(StartPoint, (EndPoint - StartPoint))
Dim FormEndStart As Integer = (html.IndexOf("</form>") - 1)
If (FormEndStart >= 0) Then
html = html.Insert(FormEndStart, viewstateInput)
End If
End If
writer.Write(html)
End Sub
End Class</source>
Trim view state
<source lang="csharp">
<%@ Page Language="C#"
AutoEventWireup="true"
CodeFile="Default.aspx.cs"
Inherits="TrimViewState" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server">
<title>Untitled Page</title>
</head> <body>
<form id="form1" runat="server">
<asp:DropDownList ID="lstBig" runat="server" EnableViewState="False"/>
<asp:Button ID="cmdSubmit" runat="server" OnClick="cmdSubmit_Click" Text="Button" />
<asp:Label ID="lblInfo" runat="server" Text=""/>
</form>
</body> </html> File: Default.aspx.cs using System; using System.Data; using System.Configuration; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; public partial class TrimViewState : System.Web.UI.Page {
protected void Page_Load(object sender, EventArgs e)
{
for (int i = 0; i < 1000; i++)
{
lstBig.Items.Add(i.ToString());
}
if (Page.IsPostBack)
{
lstBig.SelectedItem.Text = Request.Form["lstBig"];
}
}
protected void cmdSubmit_Click(object sender, EventArgs e)
{
lblInfo.Text += lstBig.SelectedItem.Text + "
";
//lblInfo.Text = Request.Form["lstBig"];
}
}</source>
Use ViewState to store object list (C#)
<source lang="csharp">
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!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>Untitled Page</title>
</head> <body>
<form id="form1" runat="server">
</form>
</body> </html> File: Default.aspx.cs using System; using System.Data; using System.Configuration; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; public partial class _Default : System.Web.UI.Page {
[Serializable]
class Person
{
public string first = "first";
public string last = "last";
public string blog = "http://www.nfex.ru";
}
protected void Page_Load(object sender, EventArgs e)
{
Person[] people = new Person[500];
for (int i = 0; i < people.Length; i++)
{
people[i] = new Person();
}
ViewState["Folks"] = people;
}
private string _pageGuid = null;
public string PageGuid
{
get
{
if (_pageGuid == null)
_pageGuid = this.Request.Form["__VIEWSTATE_KEY"];
if (_pageGuid == null)
_pageGuid = Guid.NewGuid().ToString();
return _pageGuid;
}
set
{
_pageGuid = value;
}
}
protected override object LoadPageStateFromPersistenceMedium()
{
return Session[this.PageGuid];
}
protected override void SavePageStateToPersistenceMedium(object viewState)
{
RegisterHiddenField("__VIEWSTATE_KEY", this.PageGuid);
Session[this.PageGuid] = viewState;
}
}</source>
Use ViewState to store object list (VB)
<source lang="csharp">
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %> <!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>Untitled Page</title>
</head> <body>
<form id="form1" runat="server">
</form>
</body> </html> File: Default.aspx.vb
Partial Class _Default
Inherits System.Web.UI.Page
<Serializable()> Class Person
Public first As String = "first"
Public last As String = "last"
Public blog As String = "http://www.nfex.ru"
End Class
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim people(500) As Person
For i As Integer = 0 To people.Length - 1 Step 1
people(i) = New Person
Next
ViewState("Folks") = people
End Sub
Dim _pageGuid As String = Nothing
Public Property PageGuid() As String
Get
"Do we have it already? Check the Form, this could be a post back
If (_pageGuid = Nothing) Then
_pageGuid = Me.Request.Form("__VIEWSTATE_KEY")
End If
"No? We"ll need one soon.
If (_pageGuid = Nothing) Then
_pageGuid = Guid.NewGuid.ToString
End If
Return _pageGuid
End Get
Set(ByVal value As String)
_pageGuid = value
End Set
End Property
Protected Overrides Function LoadPageStateFromPersistenceMedium() As Object
Return Session(Me.PageGuid)
End Function
Protected Overrides Sub SavePageStateToPersistenceMedium(ByVal viewState As Object)
RegisterHiddenField("__VIEWSTATE_KEY", Me.PageGuid)
Session(Me.PageGuid) = viewState
End Sub
End Class</source>
