How to POST a multipart/form-data request to a REST endpoint in a WCF service that also has SOAP endpoints

I have looked at many posts about how to accept an uploaded document in a WCF service REST endpoint. They say you should define the endpoint to have a single parameter with type Stream. Here is an example of one. I have implemented it as they suggest and it does work. Here it is in VB:

<WebInvoke(Method:="POST", BodyStyle:=WebMessageBodyStyle.Bare)>
Function UploadDocument(data As Stream) As Stream

However, I am working with the additional constraint that this WCF service also uses SOAP endpoints. After adding this REST endpoint that accepts a Stream, the SOAP endpoints are breaking. The error in the SOAP response says

System.InvalidOperationException: For request in operation UploadDocument to be a stream the operation must have a single parameter whose type is Stream.

I am new to WCF services and SOAP (unfortunately I have to use it in 2021, yay), so I was amazed that adding a REST endpoint would break these SOAP endpoints. I looked that error up and found this post. This comment from Drew Marsh seems to be the fundamental problem here:

the WSDL generator implementation is made for the SOAP/RPC service contracts and on those you can't either have individual parameters of various intrinsic or data contract types, a Stream or a message contract. You can't mix the three together. So, when it tries to generate metadata for your REST service contract, where it's perfectly valid to throw a Stream parameter in the mix as the last parameter for the body, it bombs out with the error your seeing because it never expects to come across a signature like that.

I do not see any solution on that post or anywhere else I search. I tried making a <DataContract> class which has the document as a property with type Stream, along with the other form fields as properties, but when I try that I get the error

Unhandled InvalidOperationException in service: The incoming message has an unexpected message format 'Raw'. The expected message formats for the operation are 'Xml', 'Json'. This can be because a WebContentTypeMapper has not been configured on the binding. See the documentation of WebContentTypeMapper for more details.

Am I simply SOL if I want this REST endpoint to accept a multipart/form-data body? Or is there some way to make this work with all the constraints I'm working with? In case it makes a difference, yet another constraint is that this service is stuck in .NET 4.0, so that rules out some potential libraries that need .NET 4.5.

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Content Attribution

This content was originally published by Drew at Recent Questions - Stack Overflow, and is syndicated here via their RSS feed. You can read the original post over there.

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