What is the [HttpGet] statement for? [duplicate]

Question

What is the [HttpGet] statement for? [duplicate]

Navigation

#1 by (2 votes)

0

In a given method of my Controller created in Asp Net MVC , I learned that I could put the [HttpGet] statement.

In other cases, like in my models, I realized that you can also put [Length(10)] and still other things.

I'm somewhat familiar with this in Python (of declaring things "on top" of the method).

For example:

 @app.route('/')
 def home(response):
     return template(response, 'meu_template.html')

In Python this is called decorator.

What about C #? This statement made on top of the method serves the same purpose as the decorators of Python ?

What is the name of this Syntax?

References:

How decorators work in Python?

c# python asp.net-mvc

asked by anonymous 04.05.2016 / 14:57

1 answer

Class c ++ has no member named how to do test with sql injection

score 2 · Accepted Answer

Wallace, [HttpGet] and [Length] are Attributes , which are how to implement the Decorator Pattern no .NET .

They are useful when you want to associate some additional information with your class, field, property, etc.

If you want to implement your own Attribute, simply create a class that inherits directly or indirectly from System.Attribute , as in the examples below.

[AttributeUsage(AttributeTargets.Class)]
public class ClassInfoAttribute : System.Attribute 
{    
   public string Namespace { get; set; }
   public string Name { get; set; }

   public ClassInfoAttribute()
   {
   }
}

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
public class FieldInfoAttribute : System.Attribute 
{    
   public string DataType { get; set; }
   public string Name { get; set; }

   public FieldInfoAttribute()
   {
   }
}

To use them, simply assign an attribute on your class, field, property with the name of the Attribute (without the Attribute).

[ClassInfo(Namespace = "Meu Namespace", Name = "Minha Classe")]
public class MinhaClasse
{    
   [FieldInfo(DataType = "Texto", Name = "Minha Propriedade")]
   public string MinhaPropriedade { get; set; }

   [FieldInfo(DataType = "Texto", Name = "Meu Campo")]
   public string meuCampo;

   public MinhaClasse()
   {
   }
}

If you need to retrieve the attribute, you will need to use a bit of System.Reflection

var classe = new MinhaClasse();
var tipo = classe.GetType();
var campo = tipo.GetField("meuCampo");
var propriedade = tipo.GetProperty("MinhaPropriedade");
var classIndo = (ClassInfoAttribute)tipo.GetCustomAttributes(typeof(ClassInfoAttribute), false);
var fieldInfo = (FieldInfoAttribute)campo.GetCustomAttributes(typeof(FieldInfoAttribute), false);
var propertyInfo = (FieldInfoAttribute)propriedade.GetCustomAttributes(typeof(FieldInfoAttribute), false);

Since you mentioned ASP.NET MVC , an attribute that you might know is Action Filter , so just implement the IActionFilter interface and inherit from ActionFilterAttribute .

public class MeuFiltroAttribute : ActionFilterAttribute, IActionFilter
{
    void OnActionExecuting(ActionExecutingContext filterContext) { ... }
    void OnActionExecuted(ActionExecutingContext filterContext) { ... }
    void OnResultExecuting(ResultExecutingContext filterContext) { ... }
    void OnResultExecuted(ResultExecutedContext filterContext) { ... }  
}

[MeuFiltro]
public class MinhaController : Controller
{
    ...
}