Question

I get a serialization error on a page containing a custom control. the control has a member (dataContext) of a type (EntityContext) that is non-serializable, and marked as such.

this is the error:

Type ‘Entities.EntityContext’ in
Assembly ‘…’ is not marked as
serializable.

[SerializationException: Type
‘…Entities.EntityContext’
in Assembly ‘…’ is
not marked as serializable.]
System.Runtime.Serialization.FormatterServices.InternalGetSerializableMembers(RuntimeType
type) +7733643
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(Object
obj, ISurrogateSelector
surrogateSelector, StreamingContext
context, SerObjectInfoInit
serObjectInfoInit, IFormatterConverter
converter, ObjectWriter objectWriter)
+161 System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.Serialize(Object
obj, ISurrogateSelector
surrogateSelector, StreamingContext
context, SerObjectInfoInit
serObjectInfoInit, IFormatterConverter
converter, ObjectWriter objectWriter)
+51 System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Serialize(Object
graph, Header[] inHeaders,
__BinaryWriter serWriter, Boolean fCheck) +410
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) +4966

[ArgumentException: Error serializing
value
‘…Entities.EntityContext’
of type
‘…Entities.EntityContext.’]
System.Web.UI.ObjectStateFormatter.SerializeValue(SerializerBinaryWriter
writer, Object value) +5425
System.Web.UI.ObjectStateFormatter.Serialize(Stream
outputStream, Object stateGraph) +163
System.Web.UI.ObjectStateFormatter.Serialize(Object
stateGraph) +99
System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Serialize(Object
state) +37
System.Web.UI.Util.SerializeWithAssert(IStateFormatter
formatter, Object stateGraph) +55
System.Web.UI.HiddenFieldPageStatePersister.Save()
+143 System.Web.UI.Page.SavePageStateToPersistenceMedium(Object
state) +190
System.Web.UI.Page.SaveAllState()
+1466 System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint, Boolean
includeStagesAfterAsyncPoint) +5477

This is the control:

public class EntityDataSource : ObjectDataSource
{
    [NonSerialized] private EntityContext dataContext;

    /// <summary>
    /// Gets the data context. (This is used by the page at runtime.)
    /// </summary>
    /// <value>The data context.</value>
    // ReSharper disable MemberCanBePrivate.Global
    public EntityContext DataContext
    // ReSharper restore MemberCanBePrivate.Global
    {
        get { return dataContext; }
    }

    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);
        dataContext = new EntityContext(SessionProvider.GetContext());
    }

    /// <summary>
    /// Viewstate is not implemented. This value allways return <c>false</c>.
    /// </summary>
    /// <exception cref="NotSupportedException">Exception is thrown when setting this value.</exception>
    [Browsable(false)]
    public override bool EnableViewState
    {
        get
        {
            return false;
        }
        set
        {
            //Throws exception if value is true.
            if (value)
            {
                throw new NotSupportedException("Viewstate is not enabled on this control.");
            }
        }
    }

    public override void Dispose()
    {
        if (DataContext != null)
        {
            DataContext.Dispose();
        }

        base.Dispose();
    }
}

It almost seems like the page doesn’t honor the NonSerializedAttribute.
I have omitted the company and product names from the namespaces.

Answer 1

If I am understanding the problem …

I take it the instance is beeing serialized and you wish it not to be so. Well, if you cannot change the way the instance is handled, change the way it serializes. Implement System.Runtime.Serialization.ISerializable and just set the initial state in the deserialization constructor (required when implementing the interface). This way at least you circumvent the exception (be sure this still results in correct behaviour) and you add nothing much to the stream (other than type information). As you need no state persisted, you simply do not add items to the dictionary.