AJAX History control - using with a GridView

The History control allows web applications to inject browser history checkpoints based on the state of a AJAX control.  The History control can store the state of a single serializable object, or can take a Dictionary<string, object> pairing where the string is a key identifying the serialized object.

To begin implimentation, add a <asp:History /> control to the page….

<asp:History ID="HistoryManager" runat="server" OnNavigate="HistoryManager_Navigate"></asp:History>

Then add a asyncronous trigger to the related UpdatePanel:

<Triggers>

<asp:AsyncPostBackTrigger ControlID="HistoryManager" />

</Triggers>

Once the History control has been added to the page, in your code-behind, you need to insert checkpoints as well as handle the a postback created by the browser buttons, or OnNavigate. 

First, insert checkpoints where they make sense.  This usually occurs within a partial page postback, for example a LinkButton within your UpdatePanel.  In the following example, the AddGridHistory function is called whenever I want to store a history checkpoint.  The function stores the state of a GridView by serializing every parameter needed to grab the exact data of a history checkpoint.

private void AddGridHistory()

{

Dictionary<string, object> gridState = new Dictionary<string, object>();

gridState.Add("ProductID", this.ProductID);

gridState.Add("NewerThan", this.NewerThan);

gridState.Add("SearchText", this.SearchText);

gridState.Add("SortCriteria", this.SortCriteria);

gridState.Add("SortOrder", this.SortOrder);

gridState.Add("NumberofRowsToReturn", this.NumberofRowsToReturn);

HistoryManager.AddHistoryPoint(gridState);

}

Now all we need to do is handle the OnNavigate event, which occurs when the browser Forward and Back buttons are used.  The event handler is referenced above in our <asp:History /> control.  When called, the handler will assign that state's Parameters, before the app retrieves data and DataBinds the GridView.  The handler looks like this:

public void HistoryManager_Navigate(object sender, Microsoft.Web.Preview.UI.Controls.HistoryEventArgs args)

{

if (args.State.ContainsKey("ProductID")) this.ProductID = (string)args.State["ProductID"];

if (args.State.ContainsKey("NewerThan")) this.NewerThan = (string)args.State["NewerThan"];

if (args.State.ContainsKey("SearchText")) this.SearchText = (string)args.State["SearchText"];

if (args.State.ContainsKey("SortCriteria")) this.SortCriteria = (SortCriteria)args.State["SortCriteria"];

if (args.State.ContainsKey("SortOrder")) this.SortOrder = (SortOrder)args.State["SortOrder"];

if (args.State.ContainsKey("NumberofRowsToReturn")) this.NumberofRowsToReturn = (string)args.State["NumberofRowsToReturn"];

RefreshGrid();

}