XML deserialization failing from one webAPI and not another

Question

My environment: Visual Studio 2010

I have 2 C# webAPI projects that return data to a VB client project.

API project #1: OrchardsAPI - returns lots of data perfectly.

API project #2: aspnetAPI - accesses the Microsoft aspnetdb database on my SQL server. Throws an exception when deserialized on the Client.

When I interrogate the API projects directly from my browser, the following is the first the first line each response. API#1 returns a list of cultivars used in my orchards. Note the xmlns values.

API #1:

<ArrayOfCultivarEntity xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

API #2:

<ArrayOfaspnet_RoleEntity xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.datacontract.org/2004/07/aspnetEntities">

When accessed directly from a browser, a valid xml file is displayed with records from each API. However, when I get request the data from my Client, I get an exception stating that:

InnerException  {"<ArrayOfaspnet_RoleEntity xmlns='http://schemas.datacontract.org/2004/07/aspnetEntities'> was not expected."}

The relevant code in my client is:

   Public Function GetAllRoles() As List(Of aspnetEntities.aspnet_RoleEntity)
        Dim _entities As New List(Of aspnet_RoleEntity)
        Try
            url = "role/byAppName/OrchardAutomation"
            responseMessage = client.GetAsync(url).Result
            If responseMessage.IsSuccessStatusCode = True Then
                _entities = New Xml.Serialization.XmlSerializer(_entities.GetType).Deserialize(responseMessage.Content.ReadAsStreamAsync.Result)
                Return _entities
            Else
                ProcessClientError(responseMessage.Content.ReadAsStringAsync.Result)
                Return Nothing
            End If
        Catch ex As Exception
            ProcessClientException(ex)
            Return Nothing
        End Try
    End Function

I have searched for all instances of "xmlns" in both API projects and they are all identical. There must be something I'm missing. Any hints greatly appreciated.

Answer 1

Solved thanks to the following link: [https://docs.microsoft.com/de-de/aspnet/web-api/overview/formats-and-model-binding/json-and-xml-serialization#xml_media_type_formatter]

Turns out my API #1 had the following code in the global.asax file:

GlobalConfiguration.Configuration.Formatters.XmlFormatter.MediaTypeMappings.Add(new QueryStringMapping("type", "xml", new System.Net.Http.Headers.MediaTypeHeaderValue("application/xml")));
GlobalConfiguration.Configuration.Formatters.Remove(GlobalConfiguration.Configuration.Formatters.JsonFormatter);
GlobalConfiguration.Configuration.Formatters.XmlFormatter.UseXmlSerializer = true;

The aforementioned link noted that the datacontract serializer was the default and one had to add the code to switch to the xml formatter:

var xml = GlobalConfiguration.Configuration.Formatters.XmlFormatter;
xml.UseXmlSerializer = true;

Which I put in the initialization section of my controller. That solved the problem. I then looked at the global.asax in API#1 and found the 3 lines in the app_start method. I inserted them into the app_start of API#2, removed the "var xml" lines from the initialization of the individual controller and the project continued to work perfectly.

Hope this helps someone else!