What are Filters in ASP.NET Core? See Example

Filters in ASP.NET Core allow developers to execute code before or after controller actions. They are used for cross-cutting concerns like logging, authorization, exception handling, and caching. Filters help keep controllers clean and maintainable.

Key Features:

• Execute code at different stages of request processing
• Types: Authorization, Resource, Action, Exception, and Result filters
• Can be applied globally, per controller, or per action
• Supports asynchronous operations
• Enhances modularity and maintainability

Example:
Creating a simple Action Filter:

public class LogActionFilter : IActionFilter
{
    public void OnActionExecuting(ActionExecutingContext context)
    {
        Console.WriteLine("Action executing...");
    }

    public void OnActionExecuted(ActionExecutedContext context)
    {
        Console.WriteLine("Action executed.");
    }
}

Register filter in Program.cs:

builder.Services.AddControllersWithViews(options =>
{
    options.Filters.Add<LogActionFilter>();
});

Filters in ASP.NET Core allow modular handling of cross-cutting concerns, keeping your controllers and actions clean and efficient.

Citations:

• Learn more on Savanka
• Official ASP.NET Core Documentation