更好的选择是从config中读取扩展名/ mime类型对，并将其注入到Config方法中，这样可以从配置中管理扩展名：

appsettings.json：

"StaticFilesConfig": {
    "AllowedExtensions": {
      ".apk": "application/vnd.android.package-archive",
      ".ext": "application/ext-example-mimetype" // example
    } 
  }

Startup.cs：

public void ConfigureServices(IServiceCollection services)
{
....
services.Configure<StaticFilesConfig>(Configuration.GetSection("StaticFilesConfig"));
....
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env
 , ILoggerFactory loggerFactory, IOptions<StaticFilesConfig> staticFilesConfig)
{
...
if (staticFilesConfig != null)
            {
                SetStaticFileOptions(app, staticFilesConfig);
            }
...
}

private void SetStaticFileOptions(IApplicationBuilder app
, IOptions<StaticFilesConfig> staticFilesOptions)
        {
            var mapping = staticFilesOptions.Value.AllowedExtensions;
            if (mapping != null && mapping.Any())
            {
                var provider = 
  new FileExtensionContentTypeProvider(staticFilesOptions.Value.AllowedExtensions);
                app.UseStaticFiles(new StaticFileOptions
                {
                    ContentTypeProvider = provider
                });
            }
        }
}

StaticFilesConfig.cs：

public class StaticFilesConfig
    {
        public IDictionary<string, string> AllowedExtensions { get; set; }
    }
转载至:https://serverfault.com/questions/501562/configure-iis-7-0-to-download-apk/1006056#1006056

.netCore中使用配置实现下载apk文件