CSLA 5 to 8 Stream property in Command object

[walkerboh]

Hello,

I am in the process of updating an application from CSLA 5 to 8 and I believe I've run into an issue with the retiring of the BinaryFormatter.

I have a bunch of Command objects that have Stream properties to handle a file upload.

public class CommandExample : CommandBase<CommandExample>
{
    public string Id
    {
        get { return GetProperty(IdProperty); }
        set { SetProperty(IdProperty, value); }
    }
    public static readonly PropertyInfo<int> IdProperty = RegisterProperty<int>(c => c.Id);

    public Stream FileData
    {
        get { return GetProperty(FileDataProperty); }
        set { SetProperty(FileDataProperty, value); }
    }
    public static readonly PropertyInfo<Stream> FileDataProperty = RegisterProperty<Stream>(c => c.FileData);

    [Execute]
    protected async Task DataPortal_Execute()
    {
        // ... file upload logic here
    }
}

In CSLA 5, this was working fine, but with the update to CSLA 8 I am now getting System.NotSupportedException: Serialization of type object is not supported. (Microsoft.AspNetCore.Http.ReferenceReadStream).

Is there a way I can continue to support Stream properties on these commands? Or is the better solution to just convert to byte[] when setting up the commands and converting it back to a stream when necessary?

Thank you!

[rockfordlhotka]

I'm surprised that ever worked. That's interesting to me. It must be that BinaryFormatter had a way to serialize a stream? Wow!

In any case, BinaryFormatter is now obsolete in .NET, and so we had to stop supporting or using it in CSLA as well. The only serializer in CSLA 8 is MobileFormatter, and it has its own set of serialization rules.

https://github.com/MarimerLLC/csla/blob/main/docs/serialization.md#mobileformatter-constraints

In CSLA 9 you can create what's called a custom serializer and map it to a type, so you can write your own serializer for Stream if you can figure out how such a thing would work.

I assume that what they must have done is read the entire stream into a MemoryStream so it could become a byte[] that could be transferred over the network.

[walkerboh]

Okay cool, I will check out the custom serializers, would save me having to manually to the conversion in quite a few places. Thanks!

[rockfordlhotka]

Your other option, if you need to stay at CSLA 8 for some reason, is to implement the (from memory) GetState and SetState methods used by MobileFormatter.

1. Make your property have a private backing field instead of a managed backing field
2. Override the get/set state methods
3. Get and set the stream's content into and out of the serialization stream - probably by using a MemoryStream to convert the stream into a byte[] so MobileFormatter knows how to deal with it

[walkerboh]

I'm trying to avoid make too many changes to the Command objects themselves if I don't need to. There is nothing special about the Stream property itself so if I have to make the change to the objects it might make more sense to just move to the MobileList<byte> from the streams instead of adding the serialization overhead just to keep the property type.

I don't have to stick to CSLA 8 and since it looks like 9 is built to run on .NET 8 as well, I think I can at least try it out without commiting to too much change.

[rockfordlhotka]

MobileFormatter can directly serialize byte[], so that might be the best option for the property type.

[walkerboh]

That's good to know. I got too deep with other changes I was making and didn't even think to double check that.