Using constant for defining property format in MVC

问题

In my MVC application I have many properties of DateTime datatype and I define DataFormatString on every new property in this datatype is defined as below:

Model:

[DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}", ApplyFormatInEditMode = true)]
public DateTime StartDate{ get; set; }


[DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}", ApplyFormatInEditMode = true)]
public DateTime EndDate{ get; set; }

Instead of this, I think there is another option to define these DataFormatStrings for just one place and at once by creating a new class containing constant value or using web config, etc. So, in this case what is the best way to use constant values i.e. date format, etc. I use globalization string on my web.config, but I am not sure defining date DataFormatStrings in web.config as well. Any help would be appreciated.

回答1:

I'd opt for a custom attribute

public class ShortDateFormatAttribute : DisplayFormatAttribute
{
    public ShortDateFormatAttribute()
    {
        DateFormat = "{0:dd/MM/yyyy}";
        ApplyFormatInEditMode = true;
    }
}
....
[ShortDateFormat]
public DateTime StartDate { get; set; }
[ShortDateFormat]
public DateTime EndDate { get; set; }

回答2:

There is a limitation that you are facing here - attribute parameters can be only compile-time ones. Because of this you have two options:

1. Just define a constant and use it in all the models, like this

   private const string DateFormat = "{0:dd/MM/yyyy}";
   
   [DisplayFormat(DataFormatString = DateFormat, ApplyFormatInEditMode = true)]
   

2. Define the format in web.config and create your own attribute, perhaps inheriting from DisplayFormat, that will go to web.config to retrieve necessary data. Should be really simple - you just need another constructor that will get format param from web.config. Something like that:

   public class WebConfigDateDisplayFormatAttribute : DisplayFormatAttribute
   {
       public WebConfigDateDisplayFormatAttribute()
       {
           DataFormat = System.Configuration.ConfigurationManager.AppSettings["DateFormat"];
       }
   }
   

来源：https://stackoverflow.com/questions/30255539/using-constant-for-defining-property-format-in-mvc