Asp net core filters with arguments and di

ASP.NET Core provides a powerful feature called filters that allow developers to add cross-cutting concerns to their applications. Filters are used to perform actions before or after an action method is executed, or to modify the result of an action method.

One common use case for filters is to handle authentication and authorization. By applying an authentication to a controller or action method, developers can ensure that only authenticated users can access certain parts of their application. Similarly, an authorization filter can be used to restrict access to specific roles or permissions.

use case for filters is to handle exception handling. By applying an exception filter to a controller or action method, developers can catch and handle exceptions that occur during the execution of the action method. This allows for centralized handling and the ability to return error messages or redirect the user to an error page.

Filters can also be used to perform logging, caching, and other cross-cutting concerns. By applying a filter to a controller or action method, developers can easily add additional functionality without cluttering their codebase.

Creating Custom Filters

ASP.NET Core allows developers to create custom filters by implementing the `IFilterMetadata` interface. This interface defines a single method called `OnActionExecuting`, which is called before an action method is executed. Developers can use this method to perform any necessary or modifications before the action method is executed.

Here's an example of a custom filter that logs the name of the action method before it is executed:


public  LoggingFilter : IActionFilter
{
    public void OnActionExecuting(ActionExecutingContext context)
    {
        var actionName = context.ActionDescriptor.DisplayName;
        Console.WriteLine($"Executing action: {actionName}");
    }

    public void (ActionExecutedContext context)
    {
        // Do nothing
    }
}

To apply this filter to a controller or action method, developers can use the `[ServiceFilter]` attribute. This attribute takes the type of the filter as a parameter and applies it to the controller or action method.

Dependency Injection with Filters

ASP.NET Core also supports dependency injection with filters. This means that developers can inject services or dependencies into their filters, allowing for more flexible and reusable code.

To inject a service into a filter, developers can use the `[TypeFilter]` attribute. This attribute takes the type of the filter as a parameter, along with any additional parameters required by the filter's constructor.

Here's an example of a filter that requires a logging service:


public class LoggingFilter : IActionFilter
{
    private readonly ILogger _logger;

    public LoggingFilter(ILogger logger)
    {
        _logger = logger;
    }

    public void OnActionExecuting(ActionExecutingContext context)
    {
        var actionName = context.ActionDescriptor.DisplayName;
        _logger.Log($"Executing action: {actionName}");
    }

    public void OnActionExecuted(ActionExecutedContext context)
    {
        // Do nothing
    }
}

To apply this filter to a controller or action method, developers can use the `[TypeFilter]` attribute with the required parameters:


[TypeFilter(typeof(LoggingFilter),  = new object[] { typeof(Logger) })]
public class MyController : Controller
{
    // Controller code here
}

In this example, the `LoggingFilter` requires a `Logger` instance to be injected. The `[TypeFilter]` attribute specifies the type of the filter and the required parameters.

Conclusion

ASP.NET Core filters provide a powerful way to add cross-cutting concerns to your applications. it's handling authentication, exception handling, logging, or other functionality, filters allow for centralized and reusable code.

By creating custom filters and using dependency injection, developers can easily extend the functionality of their applications and keep their codebase clean and maintainable.

Rate this post

Leave a Reply

Your email address will not be published. Required fields are marked *

Table of Contents