Change the JSON serialization settings of a single ASP.NET Core controller
Solution 1
ASP.NET Core 3.0+
You can achieve this with a combination of an Action Filter and an Output Formatter.
Things look a little different for 3.0+, where the default JSON-formatters for 3.0+ are based on System.Text.Json
. At the time of writing, these don't have built-in support for a snake-case naming strategy.
However, if you're using Json.NET with 3.0+ (details in the docs), the SnakeCaseAttribute
from above is still viable, with a couple of changes:
-
JsonOutputFormatter
is nowNewtonsoftJsonOutputFormatter
. - The
NewtonsoftJsonOutputFormatter
constructor requires an argument ofMvcOptions
.
Here's the code:
public class SnakeCaseAttribute : ActionFilterAttribute
{
public override void OnActionExecuted(ActionExecutedContext ctx)
{
if (ctx.Result is ObjectResult objectResult)
{
objectResult.Formatters.Add(new NewtonsoftJsonOutputFormatter(
new JsonSerializerSettings
{
ContractResolver = new DefaultContractResolver
{
NamingStrategy = new SnakeCaseNamingStrategy()
}
},
ctx.HttpContext.RequestServices.GetRequiredService<ArrayPool<char>>(),
ctx.HttpContext.RequestServices.GetRequiredService<IOptions<MvcOptions>>().Value));
}
}
}
ASP.NET Core 2.x
You can achieve this with a combination of an Action Filter and an Output Formatter. Here's an example of what the Action Filter might look like:
public class SnakeCaseAttribute : ActionFilterAttribute
{
public override void OnActionExecuted(ActionExecutedContext ctx)
{
if (ctx.Result is ObjectResult objectResult)
{
objectResult.Formatters.Add(new JsonOutputFormatter(
new JsonSerializerSettings
{
ContractResolver = new DefaultContractResolver
{
NamingStrategy = new SnakeCaseNamingStrategy()
}
},
ctx.HttpContext.RequestServices.GetRequiredService<ArrayPool<char>>()));
}
}
}
Using OnActionExecuted
, the code runs after the corresponding action and first checks to see if the result is an ObjectResult
(which also applies to OkObjectResult
thanks to inheritance). If it is an ObjectResult
, the filter simply adds a customised version of a JsonOutputFormatter
that will serialise the properties using SnakeCaseNamingStrategy
. The second parameter in the JsonOutputFormatter
constructor is retrieved from the DI container.
In order to use this filter, just apply it to the relevant controller:
[SnakeCase]
public class ControllerB : Controller { }
Note: You might want to create the JsonOutputFormatter
/NewtonsoftJsonOutputFormatter
ahead of time somewhere, for example - I've not gone that far in the example as that's secondary to the question at hand.
Solution 2
Ended up creating this method that I use on my end points:
{
// needed to get the same date and property formatting
// as the Search Service:
var settings = new JsonSerializerSettings
{
ContractResolver = new DefaultContractResolver()
{
NamingStrategy = new SnakeCaseNamingStrategy()
},
DateFormatString = "yyyy-MM-ddTHH:mm:ss.fffZ"
};
return Json(result, settings);
}
Solution 3
No need for action filters etc. Just override Json()
in your controller and that's it.
public class MyController : Controller
{
public override JsonResult Json(object data)
{
return base.Json(data, new JsonSerializerSettings {
// set whataever default options you want
});
}
}
Kees C. Bakker
Senior Software Developer and Team Manager for Capital ID - a leading international supplier specialized in automating and managing marketing processes (MRM, MOM), using its software platform ID Manager. Specialties: C# / ASP.Net Html / CSS jQuery / JavaScript (T)SQL Visit my blog: KeesTalksTech.com Follow me: twitter.com/KeesTalksTech LinkedIn: linkedin.com/in/keescbakker
Updated on June 19, 2022Comments
-
Kees C. Bakker almost 2 years
I'm having two controller controllers:
ControllerA
andControllerB
. The base class of each controller isController
.The
ControllerA
needs to return JSON in the default format (camelCase). TheControllerB
needs to return data in a different JSON format: snake_case.How can I implement this in ASP.NET Core 3.x and 2.1?
I've tried the
startup
with:services .AddMvc() .AddJsonOptions(options => { options.SerializerSettings.Converters.Add(new StringEnumConverter()); options.SerializerSettings.ContractResolver = new DefaultContractResolver() { NamingStrategy = new SnakeCaseNamingStrategy() }; }) .AddControllersAsServices();
But this will change the serialization for all controllers, not just for
ControllerB
. How can I configure or annotate this feature for 1 controller?