ViewStateException Class

Definition

public ref class ViewStateException sealed : Exception

[System.Serializable]
public sealed class ViewStateException : Exception

[<System.Serializable>]
type ViewStateException = class
    inherit Exception
    interface ISerializable

Public NotInheritable Class ViewStateException
Inherits Exception

Inheritance

Object

Exception

ViewStateException

Attributes

SerializableAttribute

Implements

ISerializable

Examples

The following code example demonstrates how to implement a method that deserializes a base64-encoded string and returns an ICollection collection of property settings. The Deserialize method can throw an HttpException exception that contains a ViewStateException object as an inner exception. The example shows how you can catch an HttpException exception and retrieve the properties from the ViewStateException object.

private ICollection LoadControlProperties(string serializedProperties)
{

    ICollection controlProperties = null;

    // Create an ObjectStateFormatter to deserialize the properties.
    ObjectStateFormatter formatter = new ObjectStateFormatter();

    try
    {
        // Call the Deserialize method.
        controlProperties = (ArrayList)formatter.Deserialize(serializedProperties);
    }
    catch (HttpException e)
    {
        ViewStateException vse = (ViewStateException)e.InnerException;
        String logMessage;

        logMessage = "ViewStateException. Path: " + vse.Path + Environment.NewLine;
        logMessage += "PersistedState: " + vse.PersistedState + Environment.NewLine;
        logMessage += "Referer: " + vse.Referer + Environment.NewLine;
        logMessage += "UserAgent: " + vse.UserAgent + Environment.NewLine;

        LogEvent(logMessage);

        if (vse.IsConnected)
        {
            HttpContext.Current.Response.Redirect("ErrorPage.aspx");
        }
        else
        {
            throw e;
        }
    }
    return controlProperties;
}

Private Function LoadControlProperties(ByVal serializedProperties As String) As ICollection

    Dim controlProperties As ICollection = Nothing

    ' Create an ObjectStateFormatter to deserialize the properties.
    Dim formatter As New ObjectStateFormatter()

    Try
        ' Call the Deserialize method.
        controlProperties = CType(formatter.Deserialize(serializedProperties), ArrayList)
    Catch e As HttpException
        Dim vse As ViewStateException
        Dim logMessage As String

        vse = e.InnerException

        logMessage = "ViewStateException. Path: " + vse.Path + Environment.NewLine
        logMessage += "PersistedState: " + vse.PersistedState + Environment.NewLine
        logMessage += "Referer: " + vse.Referer + Environment.NewLine
        logMessage += "UserAgent: " + vse.UserAgent + Environment.NewLine

        LogEvent(logMessage)

        If (vse.IsConnected) Then
            HttpContext.Current.Response.Redirect("ErrorPage.aspx")
        Else
            Throw e
        End If
    End Try
    Return controlProperties
End Function 'LoadControlProperties   

Remarks

If an exception occurs when the page loads the view-state information, the page creates a ViewStateException object and passes it as an inner exception within an HttpException exception. The HttpException exception is re-thrown to be handled by the application.

The ViewStateException class stores information about the exception in the Message property. If the request has permission to access the ServerVariables property, then the Message property contains the values returned from the RemoteAddress, RemotePort, UserAgent, PersistedState, Referer, and Path properties; otherwise, the Message property contains a generic view-state error message.

A view-state exception can be the result of a Message Authentication Codes (MAC) validation error. If the page attribute enableViewStateMac is set to true, view-state information is encoded with a MAC identifier. When the view-state information is posted back to the server, the page verifies the encoding to ensure that it has not been altered by the user. If the page cannot validate the MAC encoding on the view-state information, it will throw an HttpException exception with the ViewStateException object as an inner exception.

For MAC validation to succeed, the view-state information must be hashed by the same key when it is sent and received. Within a Web farm, the machine key on each server should be set to a common key.

Constructors

Properties

Methods

Events

Applies to

See also

• MachineKeySection