MVC - using enum in the DisplayAttribute of a Model class

Question

My questions is: I have an enum class as:

public enum EnumApplications
{       
    Android = 1,        
    IOS = 2
}

Also I have a Model which is for Creating a new user. a user can be defined as Active in any of these application when we create a new user.

My model is:

public class NewUserModel
{

    public int UserId { get; set; }

    [Required]
    [Display(Name = "FirstName")]
    public string FirstName { get; set; }

    [Required]
    [Display(Name = "LastName")]
    public string LastName { get; set; }

    public int ClientId { get; set; }

    [Required]
    [Display(Name = "Email")]
    [EmailAddress]
    public string EmailAddress { get; set; }

    [Display(Name = "Is Active in IOS")]
    public bool IsActiveInApp1 { get; set; }


    [Display(Name = "Is Active in Android")]
    public bool IsActiveInApp2 { get; set; }
}

What I want to do is in the: [Display(Name = "Is Active in Android")]

I want to use the enum so if the app name gets changed I don't need to change it here, something like:

EnumApplications.IOS.ToString()

Here's a screenshot for better understanding:

You can't do that. Unless you create your own custom DisplayAttribute, which doesn't make any sense. Just use the enum in your View. — ataravati
– ataravati, Commented Nov 20, 2015 at 19:50
you're attempt to do what exactly?.. embed instance data in an attribute? — Brett Caswell
– Brett Caswell, Commented Nov 20, 2015 at 19:52
What if you want to add a new app to the enum? You should be more concerned about that than changing the name of an app. — ataravati
– ataravati, Commented Nov 20, 2015 at 20:13

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

"I want to use the enum so if the app name gets changed I don't need to change it here"

No, there is no easy way to do this.

the only implementation I can think of (aside from runtime assembly/type compiling and generation) that you could do that, is a T4 template. the template would generate the model, and you would have to run it after modifying your enum.

in regards to your question title and comment:

MVC - Using Enum In The DisplayAttribute of a Model class

what I want is in my model instead of saying [Display(Name = "Is Active in IOS")] and hardcoding IOS. I want to get the name of IOS from my enum.

The following solution (which isn't T4 or Runtime compiling) just inherits DisplayNameAttribute and uses the constructor of your type to pass the parameter to the base type.

It is a solution in the sense that if you were to change Android to Andy you would use a refactor tool ( built-in intellisense tool these days) to implement that change across code files that references that value type.

public enum MyEnum
{
    NotSet = 0,
    iOS = 1,
    Android = 2
}

class MyDisplayNameAttribute : System.ComponentModel.DisplayNameAttribute
{
    public MyDisplayNameAttribute(MyEnum myEnum)
        : base("Is Active in " + myEnum.ToString())
    { 

    }

    public override string DisplayName
    {
        get
        {
            // you could do the "Is Active in " here, but I doubt control frameworks would use it.
            return base.DisplayName;                
        }
    }         
}

public class MyModel
{
    [MyDisplayName(MyEnum.iOS)]
    bool IsActiveApp1 { get; set; }

    // uses standard 'DisplayNameAttribute' type for test below
    [System.ComponentModel.DisplayName("Is Active in Android")]
    bool IsActiveApp2 { get; set; }
}

For quick testing, we'll do what control frameworks do, reflect over the provided type and get the CustomAttribute.. note that there is more type checking involved, we'll casting it to DisplayNameAttribute for brevity.

string[] PropertyNames = new string[] { "IsActiveApp1", "IsActiveApp2" };
System.Type MyModelInfo = typeof(MyModel);
       
PropertyNames.SelectMany(prop => MyModelInfo.GetProperty(prop).GetCustomAttributes(true))
    .ToList().ForEach((attr) =>
        {
             Console.WriteLine(((System.ComponentModel.DisplayNameAttribute)attr).DisplayName);
        });

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Nov 20, 2015 at 20:14

Brett Caswell

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3 Comments

Siva Gopal Over a year ago

I think OP needs to get the application name inside customer attribute dynamically from db/session or wherever it is stored. Otherwise why can't he directly put some const (constant) and get the work done?

Brett Caswell Over a year ago

@SivaGopal perhaps the values are populated from db/session or whatever.. but that doesn't really have anything to do with how the name is displayed by a control..

Brett Caswell Over a year ago

the purpose of the OP, as he explained it in comments.. it to do DisplayName("Is Active in " + Enum) vs DisplayName("Is Active in <Value>") .. it is a pre-compilation concern.. and it doesn't depict the value of the property.. just associates the property to a display name

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