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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;

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")]
 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)]