Unable to serialize the session state

i'm using 'StateServer' mode in ASP.NET, and i'm storing the dataset into a session object, for example i've a button which validates the calculation so i get the dataset from session object and work on it then put it back again to the same session object the procedure i think works but as we know the btn always do the postback, so i guess when that post back affect i get this error below...

Unable to serialize the session state. In 'StateServer' and 'SQLServer' mode, ASP.NET will serialize the session state objects, and as a result non-serializable objects or MarshalByRef objects are not permitted. The same restriction applies if similar serialization is done by the custom session state store in 'Custom' mode.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Web.HttpException: Unable to serialize the session state. In 'StateServer' and 'SQLServer' mode, ASP.NET will serialize the session state objects, and as a result non-serializable objects or MarshalByRef objects are not permitted. The same restriction applies if similar serialization is done by the custom session state store in 'Custom' mode.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[SerializationException: Type 'System.Web.UI.WebControls.TextBox' in Assembly 'System.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' is not marked as serializable.]
System.Runtime.Serialization.FormatterServices.InternalGetSerializableMembers(RuntimeType type) +9444601
System.Runtime.Serialization.FormatterServices.GetSerializableMembers(Type type, StreamingContext context) +247
System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitMemberInfo() +160
System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitSerialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter, ObjectWriter objectWriter, SerializationBinder binder) +218
System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.Serialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter, ObjectWriter objectWriter, SerializationBinder binder) +54
System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Serialize(Object graph, Header[] inHeaders, __BinaryWriter serWriter, Boolean fCheck) +542
System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph, Header[] headers, Boolean fCheck) +133
System.Web.Util.AltSerialization.WriteValueToStream(Object value, BinaryWriter writer) +1762

[HttpException (0x80004005): Unable to serialize the session state. In 'StateServer' and 'SQLServer' mode, ASP.NET will serialize the session state objects, and as a result non-serializable objects or MarshalByRef objects are not permitted. The same restriction applies if similar serialization is done by the custom session state store in 'Custom' mode.]
System.Web.Util.AltSerialization.WriteValueToStream(Object value, BinaryWriter writer) +1847
System.Web.SessionState.SessionStateItemCollection.WriteValueToStreamWithAssert(Object value, BinaryWriter writer) +34
System.Web.SessionState.SessionStateItemCollection.Serialize(BinaryWriter writer) +638
System.Web.SessionState.SessionStateUtility.Serialize(SessionStateStoreData item, Stream stream) +244
System.Web.SessionState.SessionStateUtility.SerializeStoreData(SessionStateStoreData item, Int32 initialStreamSize, Byte[]& buf, Int32& length, Boolean compressionEnabled) +67
System.Web.SessionState.OutOfProcSessionStateStore.SetAndReleaseItemExclusive(HttpContext context, String id, SessionStateStoreData item, Object lockId, Boolean newItem) +114
System.Web.SessionState.SessionStateModule.OnReleaseState(Object source, EventArgs eventArgs) +807
System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +148
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +75

Tags: Visual Basic, ASP.NET, ASP.NET4.0