asp.net See the following example: To display a list of items on a Web page, each user needs a different sort of list. The list of items is static, so you can bind these pages to the same cached dataset, which is only a small part of the user-specific UI state. ViewState is ideal for storing this type of value. The code is as follows:
[Visual Basic]
<%@ Import namespace= "System.Data"%>
<HTML>
<HEAD>
<title> viewstate/title> for page UI state values
</HEAD>
<body>
<form runat= "Server" >
<H3>
Storing non-control state in ViewState
</H3>
<P>
This example stores the current sort order for a column of static data in ViewState. <br>
Click the link in the column header to sort the data by that field. <br>
Clicking the link again will be sorted in reverse order.
<br><br><br>
<asp:datagrid id= "DATAGRID1" runat= "Server"
Onsortcommand= "Sortgrid" borderstyle= "None" borderwidth= "1px"
Bordercolor= "#CCCCCC" backcolor= "White" cellpadding= "5" allowsorting= "True" >
Backcolor= "#006699" >
</HeaderStyle>
</asp:datagrid>
</P>
</form>
</body>
</HTML>
<script runat= "Server" >
' Tracking SortField properties in ViewState
Property SortField () as String
Get
Dim o as Object = ViewState ("SortField")
If O is nothing Then
Return String.Empty
End If
return CStr (o)
End Get
Set (Value as String)
If Value = SortField Then
' Same as current sort file, toggle sort Direction
SortAscending = Not sortascending
End If
ViewState ("SortField") = Value
End Set
End Property
' Tracking sortascending properties in ViewState
Property sortascending () as Boolean
Get
Dim o as Object = ViewState ("sortascending")
If O is nothing Then
Return True
End If
return CBool (o)
End Get
Set (Value as Boolean)
ViewState ("sortascending") = Value
End Set
End Property
Private Sub Page_Load (sender as Object, e as EventArgs) Handles MyBase.Load
If not Page.IsPostBack Then
Bindgrid ()
End If
End Sub
Sub Bindgrid ()
' Get Data
Dim DS as New DataSet ()
Ds. READXML (Server.MapPath ("Testdata.xml"))
Dim DV as New DataView (ds. Tables (0))
' Apply sort filters and Directions
Dv. Sort = SortField
If not sortascending Then
Dv. Sort + = "DESC"
End If
' Bind grid
DataGrid1.DataSource = DV
Datagrid1.databind ()
End Sub
Private Sub Sortgrid (sender as Object, E as DataGridSortCommandEventArgs)
Datagrid1.currentpageindex = 0
SortField = E.sortexpression
Bindgrid ()
End Sub
</script>
[C #]
<%@ Page language= "C #"%>
<%@ Import namespace= "System.Data"%>
<HTML>
<HEAD>
<title> viewstate</title> for page UI state values
</HEAD>
<body>
<form runat= "Server" >
<H3>
Storing non-control state in ViewState
</H3>
<P>
This example stores the current sort order for a column of static data in ViewState. <br>
Click the link in the column header to sort the data by that field. <br>
Clicking the link again will be sorted in reverse order.
<br><br><br>
<asp:datagrid id= "DATAGRID1" runat= "Server" onsortcommand= "Sortgrid"
Borderstyle= "None" borderwidth= "1px" bordercolor= "#CCCCCC"
Backcolor= "White" cellpadding= "5" allowsorting= "True" >
</HeaderStyle>
</asp:datagrid>
</P>
</form>
</body>
</HTML>
<script runat= "Server" >
Tracking SortField Properties in ViewState
String SortField {
get {
Object o = viewstate["SortField"];
if (o = = null) {
return String.Empty;
}
Return (string) O;
}
set {
if (value = = SortField) {
Same as the current sort file, toggle the sort direction
SortAscending =! sortascending;
}
viewstate["SortField"] = value;
}
}
Tracking SortAscending Properties in ViewState
BOOL SortAscending {
get {
Object o = viewstate["sortascending"];
if (o = = null) {
return true;
}
return (BOOL) O;
}
set {
viewstate["sortascending"] = value;
}
}
void Page_Load (object sender, EventArgs e) {
if (! Page.IsPostBack) {
Bindgrid ();
}
}
void Bindgrid () {
Get Data
DataSet ds = new DataSet ();
Ds. READXML (Server.MapPath ("Testdata.xml"));
DataView dv = new DataView (ds. Tables[0]);
Apply sorting filters and orientations
Dv. Sort = SortField;
if (! sortascending) {
Dv. Sort = = "DESC";
}
Bound grid
DataGrid1.DataSource = DV;
Datagrid1.databind ();
}
void Sortgrid (object sender, DataGridSortCommandEventArgs e) {
Datagrid1.currentpageindex = 0;
SortField = e.sortexpression;
Bindgrid ();
}
</script>
The following are the Testdata.xml code referenced in the two preceding snippets:
<?xml version= "1.0" standalone= "yes"?>
<NewDataSet>
<Table>
<pub_id>0736</pub_id>
<pub_name>new Moon books</pub_name>
<city>Boston</city>
<state>MA</state>
<country>USA</country>
</Table>
<Table>
<pub_id>0877</pub_id>
<pub_name>binnet & Hardley</pub_name>
<city>Washington</city>
<state>DC</state>
<country>USA</country>
</Table>
<Table>
<pub_id>1389</pub_id>
<pub_name>algodata infosystems</pub_name>
<city>Berkeley</city>
<state>CA</state>
<country>USA</country>
</Table>
<Table>
<pub_id>1622</pub_id>
<pub_name>five Lakes publishing</pub_name>
<city>Chicago</city>
<state>IL</state>
<country>USA</country>
</Table>
<Table>
<pub_id>1756</pub_id>
<pub_name>ramona publishers</pub_name>
<city>Dallas</city>
<state>TX</state>
<country>USA</country>
</Table>
<Table>
<pub_id>9901</pub_id>
<pub_name>GGG&G</pub_name>
<city>Muenchen</city>
<country>Germany</country>
</Table>
<Table>
<pub_id>9952</pub_id>
<pub_name>scootney books</pub_name>
<city>new york</city>
<state>NY</state>
<country>USA</country>
</Table>
<Table>
<pub_id>9999</pub_id>
<pub_name>lucerne publishing</pub_name>
<city>Paris</city>
<country>France</country>
</Table>
</NewDataSet>
