How can I use filters in ASP.NET MVC?

How can I use filters in ASP.NET MVC?

In ASP.NET MVC, filters are used to execute code before or after an action method runs. You can use built-in filters like Authorization, Action, Result, and Exception filters, or create custom ones.

Can you give me an example of a custom action filter?

Sure! Here's a simple example of a custom action filter that logs the execution time of an action method:

public class LogExecutionTimeAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        // Code to log the start time
        var startTime = DateTime.Now;
        filterContext.HttpContext.Items["StartTime"] = startTime;
    }

    public override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        // Code to log the execution time
        var startTime = (DateTime)filterContext.HttpContext.Items["StartTime"];
        var executionTime = DateTime.Now - startTime;
        // Log executionTime
    }
}

How do I register this custom filter globally?

You can register your custom filter globally in the FilterConfig.cs file. Just add it to the GlobalFilters.Filters collection like this:

public class FilterConfig
{
    public static void RegisterGlobalFilters(GlobalFilterCollection filters)
    {
        filters.Add(new HandleErrorAttribute());
        filters.Add(new LogExecutionTimeAttribute()); // Register your custom filter here
    }
}

What are some common built-in filters in ASP.NET MVC?

Some common built-in filters include:

1. Authorization Filters - for user authentication and authorization.
2. Action Filters - for code that runs before or after an action method.
3. Result Filters - for code that runs before or after the result is executed.
4. Exception Filters - for handling exceptions that occur during action execution.