Serialization problem

Type 'System.Web.UI.Control' in Assembly 'System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' is not marked as serializable.
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.Runtime.Serialization.SerializationException: Type 'System.Web.UI.Control' in Assembly 'System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' is not marked as serializable.

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.Control' in Assembly 'System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' is not marked as serializable.]
   System.Runtime.Serialization.FormatterServices.InternalGetSerializableMembers(RuntimeType type) +7731563
   System.Runtime.Serialization.FormatterServices.GetSerializableMembers(Type type, StreamingContext context) +258
   System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitMemberInfo() +111
   System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitSerialize(Type objectType, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter) +283
   System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.Serialize(Type objectType, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter) +45
   System.Runtime.Serialization.Formatters.Binary.ObjectWriter.WriteArray(WriteObjectInfo objectInfo, NameInfo memberNameInfo, WriteObjectInfo memberObjectInfo) +178
   System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Write(WriteObjectInfo objectInfo, NameInfo memberNameInfo, NameInfo typeNameInfo) +7629304
   System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Serialize(Object graph, Header[] inHeaders, __BinaryWriter serWriter, Boolean fCheck) +461
   System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph, Header[] headers, Boolean fCheck) +134
   System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph) +13
   System.Web.UI.ObjectStateFormatter.SerializeValue(SerializerBinaryWriter writer, Object value) +842

[ArgumentException: Error serializing value 'System.Collections.ObjectModel.Collection`1[System.Web.UI.Control]' of type 'System.Collections.ObjectModel.Collection`1[[System.Web.UI.Control, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]].']
   System.Web.UI.ObjectStateFormatter.SerializeValue(SerializerBinaryWriter writer, Object value) +3319
   System.Web.UI.ObjectStateFormatter.Serialize(Stream outputStream, Object stateGraph) +110
   System.Web.UI.ObjectStateFormatter.Serialize(Object stateGraph) +57
   System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Serialize(Object state) +4
   System.Web.UI.Util.SerializeWithAssert(IStateFormatter formatter, Object stateGraph) +37
   System.Web.UI.HiddenFieldPageStatePersister.Save() +79
   System.Web.UI.Page.SavePageStateToPersistenceMedium(Object state) +105
   System.Web.UI.Page.SaveAllState() +236
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1099