Best and Recommended ASP.NET Hosting Tutorial – FluentFilters for ASP.NET Core | In this post we will a library for ASP.NET Core, that will add support of criteria for global action filters. ASP.NET Core have ability to register filters globally. It’s works great, but sometimes it would be nice to specify conditions for filter execution and FluentFlters will help with this task.


Project on GitHub:

What should you do ?

First Install package

For ASP.NET Core Web Application you should use FluentFilter version 0.3.* and higher. Currently latest version 0.3.0-beta.
To install the latest package you can use Nuget Package Manager in Visual Studio or specify dependency in project.json file as shown below and call for package restore.


After installing the package to your ASP.NET Core Web Application you should replace default filter provider by custom from library. Your Startup class should looks like shown below:

Registering filters

To register filters with criteria, you need do it in usual way but calling extended methods Add or AddService. Below you can see signature of these methods.

Specify conditions

To specify the conditions, you should set the chain of criteria for the filter at registration. Using criteria, you can set whether to execute a filter or not. The library already provides three criteria for use:

  • ActionFilterCriteria – filter by specified action
  • AreaFilterCriteria – filter by specified area
  • ControllerFilterCriteria – filter by specified controller

For one filter, you can only specify two chains of criteria. These are the chains of criteria that are required and which should be excluded.

Chains of criteria are constructed by using the methods And(IFilterCriteria criteria) and Or(IFilterCriteria criteria), which work as conditional logical operators && and ||.

If using the C# language, then the code above can be understood as (like pseudocode):

Implementation of custom criteria

To create a custom criterion you should inherit your class from the FluentFilters.IFilterCriteria interface and implement only one method Match with logic to making decision about filter execution. As example, look to the source code for ActionFilterCriteria: