# Saving the viewstate of RadControls server-side

## How to

Save the viewstate of RadControls server-side

## Solution

We use a common approach to store our RadControls ViewState and you shouldn't have any problems storing it on the server (when the **EnableViewState** property for the page in which the control(s) reside is set to **True**). Our products can also work with custom ViewStateManager classes - just keep in mind that the .**aspx** web form in which the control(s) is(are) placed should extend from the **BasePage** class,  e.g.

> caption BasePage.cs

```C#
using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;

using System.Text;
using System.IO;


namespace ServerSideViewstate
{
	public class BasePage : System.Web.UI.Page
	{
		//Setup the name of the hidden field on the client for storing the viewstate key
		public const string VIEW_STATE_FIELD_NAME = "__VIEWSTATE";
		
		//Setup a formatter for the viewstate information
		private LosFormatter _formatter = null;		
		
		public BasePage()
		{
		}

		//overriding method of Page class
		protected override object LoadPageStateFromPersistenceMedium()
		{
			//If server side enabled use it, otherwise use original base class implementation
			if (true == viewStateSvrMgr.GetViewStateSvrMgr().ServerSideEnabled)
			{
				return LoadViewState();
			}
			else
			{
				return base.LoadPageStateFromPersistenceMedium();
			}
		}

		//overriding method of Page class
		protected override void SavePageStateToPersistenceMedium(object viewState)
		{
			if (true == viewStateSvrMgr.GetViewStateSvrMgr().ServerSideEnabled)
			{
				SaveViewState(viewState);
			}
			else
			{
				base.SavePageStateToPersistenceMedium(viewState);
			}
		}

		//implementation of method
		private object LoadViewState()
		{
			if (_formatter == null)
			{
				_formatter = new LosFormatter();
			}

			//Check if the client has form field that stores request key
			if (null == Request.Form[VIEW_STATE_FIELD_NAME])
			{
				//Did not see form field for viewstate, return null to try to continue (could log event...)
				return null;
			}

			//Make sure it can be converted to request number (in case of corruption)
			long lRequestNumber = 0;
			try
			{
				lRequestNumber = Convert.ToInt64(Request.Form[VIEW_STATE_FIELD_NAME]);
			}
			catch
			{
				//Could not covert to request number, return null (could log event...)
				return null;
			}

			//Get the viewstate for this page
			string _viewState = viewStateSvrMgr.GetViewStateSvrMgr().GetViewState(lRequestNumber);
			
			//If find the viewstate on the server, convert it so ASP.Net can use it
			if(_viewState == null)
				return null;
			else
				return _formatter.Deserialize(_viewState);
		}


		//implementation of method
		private void SaveViewState(object viewState)
		{
			if(_formatter == null)
			{
				_formatter = new LosFormatter();
			}

			//Save the viewstate information
			StringBuilder _viewState = new StringBuilder();
			StringWriter _writer = new StringWriter(_viewState);
			_formatter.Serialize(_writer,viewState);
			long lRequestNumber = viewStateSvrMgr.GetViewStateSvrMgr().SaveViewState(_viewState.ToString());

			//Need to register the viewstate hidden field (must be present or postback things don't 
			// work, we use in our case to store the request number)
			RegisterHiddenField(VIEW_STATE_FIELD_NAME, lRequestNumber.ToString());
		}
	}
}
```

> caption viewStateSvrMgr.cs

```C#
using System;
using System.Collections;
using System.Configuration;

namespace ServerSideViewstate
{
	public class viewStateSvrMgr
	{
		// This uses an array and mod to cycle repeatedly through an array (so limited size)

		//WARNING:  When the user uses the "back" button on the browser, IE will not rerequest the page, so 
		// if the user posts again they need the viewstate to still be present on the server.  Need to set the VIEW_STATE_NUM_PAGES
		// to a tradeoff of number of back pages allowed and 
		// the amount of memory consumed by the viewstate kept per page.  
		private const short VIEW_STATE_NUM_PAGES = 5;		//Number of pages to keep viewstate for

		//Name of storage location for veiwstate information
		private const string SESSION_VIEW_STATE_MGR = "VIEW_STATE_MGR";

		private long lPageCount = 0;	//Number of pages seen by this customer 
		private string[] ViewStates = new string[VIEW_STATE_NUM_PAGES];	//Store for viewstates

		//Determine if server side is enabled or not from web.config file
		public bool ServerSideEnabled
		{
			get
			{
				//Not a problem if someone changes the value in web.config, because new AppDomain will
				// be started and all in process session is lost anyway
				return Convert.ToBoolean(ConfigurationSettings.AppSettings["ServerSideViewState"]);
			}
		}

		public viewStateSvrMgr()
		{
		}

		public long SaveViewState(string szViewState)
		{
			//Increment the total page seen counter
			lPageCount++;

			//Now use the modulas operator (%) to find remainder of that and size of viewstate storage, this creates a
			// circular array where it continually cycles through the array index range (effectively keeps
			// the last requests to match size of storage)
			short siIndex = (short)(lPageCount % VIEW_STATE_NUM_PAGES);

			//Now save the viewstate for this page to the current position.  
			ViewStates[siIndex] = szViewState;

			return lPageCount;
		}


		public string GetViewState(long lRequestNumber)
		{
			//Could cycle though the array and make sure that the given request number is actually
			// present (in case the array is not big enough).  Much faster to just take the
			// given request number and recalculate where it should be stored
			short siIndex = (short)(lRequestNumber % VIEW_STATE_NUM_PAGES);

			return ViewStates[siIndex];
		}


		public static viewStateSvrMgr GetViewStateSvrMgr()
		{
			viewStateSvrMgr oViewStateMgr;

			//Check if already created the order object in session
			if (null == System.Web.HttpContext.Current.Session[SESSION_VIEW_STATE_MGR])
			{
				//Not already in session, create a new one and put in session
				oViewStateMgr = new viewStateSvrMgr();
				System.Web.HttpContext.Current.Session[SESSION_VIEW_STATE_MGR] = oViewStateMgr;
			}
			else
			{
				//Return the session order
				oViewStateMgr = (viewStateSvrMgr)System.Web.HttpContext.Current.Session[SESSION_VIEW_STATE_MGR];
			}
			
			return oViewStateMgr;
		}
	}
}
```

> caption Default.aspx

```ASPX
<telerik:RadToolBar ID="RadToolBar1" Runat="server" 
	onbuttonclick="RadToolBar1_ButtonClick">
<CollapseAnimation Type="OutQuint" Duration="200"></CollapseAnimation>
	<Items>
		<telerik:RadToolBarButton runat="server" CheckOnClick="true" Text="Button 0">
		</telerik:RadToolBarButton>
		<telerik:RadToolBarButton runat="server" CheckOnClick="true" Text="Button 1">
		</telerik:RadToolBarButton>
		<telerik:RadToolBarButton runat="server" CheckOnClick="true" Text="Button 2">
		</telerik:RadToolBarButton>
	</Items>
</telerik:RadToolBar>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
```

```C#
protected void RadToolBar1_ButtonClick(object sender, Telerik.Web.UI.RadToolBarEventArgs e)
{
	Label1.Text = e.Item.Text;
}
```

And you should place the following lines in your web-application Web.config file:

```
<appSettings> 
    <add key="ServerSideViewState" value="true" /> 
</appSettings> 
```

For additional information concerning the custom viewstate manager usage please review the following online article:

<http://aspalliance.com/articleViewer.aspx?aId=72&vId=1&pId>

An alternative approach is discussed in this article on the CodeProject site:

<http://www.codeproject.com/KB/aspnet/ViewStatePersistance.aspx>