Increasing the ASP.NET Core upload limit for a specific endpoint via attribute
By default, ASP.NET Core limits the max request body size to 30 MB. The limit can be increased by using a middleware, or global Kestrel configuration, as described in the linked issue. What happens if you don't want to globally increase the limit, but just for a single endpoint? The same configuration can be packaged into an attribute, and the size limit can even be made dependent of an IConfiguration value.
using Microsoft.AspNetCore.Http.Features;
using Microsoft.AspNetCore.Mvc.Filters;
namespace IncreaseUploadLimitDemo;
[AttributeUsage(AttributeTargets.Method)]
public class UploadSizeLimitFilter(string appSettingsConfigName) : Attribute, IAuthorizationFilter
{
public void OnAuthorization(AuthorizationFilterContext context)
{
var configuration = context.HttpContext.RequestServices.GetService<IConfiguration>();
if (configuration?.GetValue<long?>(appSettingsConfigName) is not { } maxRequestBodySize) return;
if (context.HttpContext.Features.Get<IHttpMaxRequestBodySizeFeature>() is { } maxRequestBodySizeFeature)
{
maxRequestBodySizeFeature.MaxRequestBodySize = maxRequestBodySize;
}
}
}An IAuthorizationFilter is used because IHttpMaxRequestBodySizeFeature.MaxRequestBodySize can only be set as long as the request has not been read yet, which is the case for a regular IActionFilter for example.
Assuming the configuration value name MaxRequestBodySize has been set in appsettings.json similar to this:
{
"Logging": {
"LogLevel": {
"Default": "Information",
"Microsoft.AspNetCore": "Warning"
}
},
"AllowedHosts": "*",
"MaxRequestBodySize": 500000000
}
an endpoint can now be annotated with the previously implemented attribute:
[HttpGet(Name = "GetWeatherForecast")]
[UploadSizeLimitFilter("MaxRequestBodySize")]
public IEnumerable<WeatherForecast> Get()
{
return Enumerable.Range(1, 5).Select(index => new WeatherForecast
{
Date = DateOnly.FromDateTime(DateTime.Now.AddDays(index)),
TemperatureC = Random.Shared.Next(-20, 55),
Summary = Summaries[Random.Shared.Next(Summaries.Length)]
})
.ToArray();
}