Why won't my ASP.Net Core Web API Controller return XML?

Question

I have the following simple Web API controller:

    // GET: api/customers
    [HttpGet]
    public async Task Get()
        {
        var         


        

Answer 1

For asp.net core 2.x, you can configure OutputFormatter.

you can try following code pieces in startup.cs class ConfigureServices method.

public void ConfigureServices(IServiceCollection services)
{
     services.AddMvc(action =>
     {
         action.ReturnHttpNotAcceptable = true;
         action.OutputFormatters.Add(new XmlDataContractSerializerOutputFormatter());
     });

     //...
}

For using XmlDataContractSerializerOutputFormatter references from Microsoft.AspNetCore.Mvc.Formatters package from nuget.

now it should work for xml and json

Answer 2

For MVC 1.1 you need to add the Package Microsoft.AspNetCore.Mvc.Formatters.Xml and edit your Startup.cs:

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc(options => { options.RespectBrowserAcceptHeader = true; })
        .AddXmlSerializerFormatters()
        .AddXmlDataContractSeria‌​lizerFormatters();
}

Now you can set the Accept Header:

XML: application/xml

JSON: application/json

Answer 3

Xml formatters are part of a separate package: Microsoft.AspNetCore.Mvc.Formatters.Xml

Add the above package and update your startup.cs like below:

services
    .AddMvc()
    .AddXmlDataContractSerializerFormatters();

OR

services
    .AddMvc()
    .AddXmlSerializerFormatters();

Answer 4

For Core 2.x versions, you have to do two things. First thing is you need to add following code inside the ConfigureServices method of Startup.cs file.

services.AddMvc()
.AddMvcOptions(o => o.OutputFormatters.Add(
    new XmlDataContractSerializerOutputFormatter())
);

And then add the Accept "application/xml" header to the request as below on Postman. Then XML formatted result will be returned.

Answer 5

For Asp.Net Core 2.x you basically need these 3 things in order to return an XML response:

Startup.cs:

services
    .AddMvcCore(options => options.OutputFormatters.Add(new XmlSerializerOutputFormatter())

CustomerController.cs:

using Microsoft.AspNetCore.Mvc;

namespace WebApplication
{
    [Route("api/[controller]")]
    public class CustomerController : ControllerBase
    {
        [HttpGet]
        public IActionResult Get()
        {
            var customer = new CustomerDto {Id = 1, Name = "John", Age = 45};
            return Ok(customer);
        }
    }
}

CustomerDto.cs:

namespace WebApplication
{
    public class CustomerDto
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
    }
}

And then upon adding the Accept "application/xml" header to the request an XML formatted result will be returned.

A very important note that I had to find out for myself is if your model does not have an implicit of explicit parameterless constructor then the response will be written as a json. Given the following example

namespace WebApplication
{
    public class CustomerDto
    {
        public CustomerDto(int id, string name, int age)
        {
            Id = id;
            Name = name;
            Age = age;
        }

         public int Id { get; }
         public string Name { get; }
         public int Age { get; }
    }
}

It would return json. To this model you should add

public CustomerDto()
{
}

And that would again return XML.

Answer 6

The following solution worked for me nicely.

At Startup.cs

services.AddMvc()
       .AddXmlSerializerFormatters()
       .AddXmlDataContractSerializerFormatters();

At YourController.cs

    [HttpGet]
    [Route("Get")]
    [Produces("application/xml")] // If you don't like to send Content-Type header
    public IActionResult Get()
    {
        try
        {                
            var user = _userManager.FindByNameAsync('user').Result;
            if (user != null)
            {
                if (!_userManager.CheckPasswordAsync(user, 'password').Result)
                {
                    return Unauthorized();
                }
                else
                {
                    var result = _services.GetDataFromService(Convert.ToInt64(2), start_date, end_date);
                    return Ok(result);
                }
            }
            else
            {
                return Unauthorized();
            }
        }
        catch (Exception ex)
        {
            return Unauthorized();
        }
    }