Problem Details as XML

[csuzw]

I'm working on a .net 10 minimal api which on error returns Problem Details responses. There is an endpoint that needs to respond with XML. Is it possible to get a Problem Details response returned as XML and if so how? If I set the Accept header to application/xml I get no contents in the response at all.

[engineering87]

Hello @csuzw,
tot by default.
AddProblemDetails() gives you Problem Details generation, but it doesn’t by itself make Minimal APIs return them as XML. XML support in ASP.NET Core comes from MVC formatters, so if you need application/xml you have to register XML formatters, for example with AddControllers().AddXmlSerializerFormatters().
In Minimal APIs, if you return HttpResults, content negotiation isn’t fully available the same way it is in MVC, and the result type decides the response content type. So Accept: application/xml won’t automatically give you an XML Problem Details payload.
If you need XML errors for that endpoint, the only options are either to go through MVC with XML formatters enabled, or return a custom XML error payload yourself.

[mr-baraiya]

By default, ProblemDetails responses in Minimal APIs are returned as JSON. Even if you call AddProblemDetails(), XML formatting is not enabled automatically.

If you need XML responses, you must register XML formatters. One way is to add MVC services:

builder.Services
    .AddControllers()
    .AddXmlSerializerFormatters();

However, Minimal API HttpResults do not fully support content negotiation like MVC controllers. If the endpoint must return XML ProblemDetails, another option is to manually serialize the object to XML and return it with the correct content type.

So in practice, XML ProblemDetails typically requires either:

• using MVC controllers with XML formatters, or
• returning a custom XML response from the endpoint.