With EntityFramework, how to access DisplayName for foreign key columns?

Question

I have the following annotations :

    [Display(Name = "NotImportant", ResourceType = typeof(MyResxFile))]
    public int? PhoneModel { get; set; } // this is the id
    [Display(Name = "Important", ResourceType = typeof(MyResxFile))]
    public virtual PhoneModel PhoneModel1 { get; set; } // this is the object

I use the following method to get the display name :

    PropertyInfo pi = SomeObject.GetProperties[0]; // short example
    columnName = ReflectionExtensions.GetDisplayName(pi);

It works for all columns except the code finds no custom/display attribute for columns such as PhoneModel1 even if there is clearly one attribute. It works for the int? but I don't need the header for the id, I need the header for the actual value, which is in PhoneModel1.

    public static class ReflectionExtensions
    {

        public static T GetAttribute<T>(this MemberInfo member, bool isRequired)
            where T : Attribute
        {
            var attribute = member.GetCustomAttributes(typeof(T), false).SingleOrDefault();

            if (attribute == null && isRequired)
            {
                throw new ArgumentException(
                    string.Format(
                        CultureInfo.InvariantCulture,
                        "The {0} attribute must be defined on member {1}",
                        typeof(T).Name,
                        member.Name));
            }

            return (T)attribute;
        }

        public static string GetDisplayName(PropertyInfo memberInfo)
        {
            var displayAttribute = memberInfo.GetAttribute<DisplayAttribute>(false);

            if (displayAttribute != null)
            {
                ResourceManager resourceManager = new ResourceManager(displayAttribute.ResourceType);
                var entry = resourceManager.GetResourceSet(Thread.CurrentThread.CurrentUICulture, true, true)
                                           .OfType<DictionaryEntry>()
                                           .FirstOrDefault(p => p.Key.ToString() == displayAttribute.Name);

                return entry.Value.ToString();
            }
            else
            {
                var displayNameAttribute = memberInfo.GetAttribute<DisplayNameAttribute>(false);
                if (displayNameAttribute != null)
                {
                    return displayNameAttribute.DisplayName;
                }
                else
                {
                    return memberInfo.Name;
                }
            }
        }
    }

Answer 1

Your GetDisplayName extension method should look like this:

public static string GetDisplayName(this PropertyInfo pi)
{
    if (pi == null)
    {
        throw new ArgumentNullException(nameof(pi));
    }
    return pi.IsDefined(typeof(DisplayAttribute)) ? pi.GetCustomAttribute<DisplayAttribute>().GetName() : pi.Name;
}

And to use it:

PropertyInfo pi = SomeObject.GetProperties[0];
string columnName = pi.GetDisplayName();

Note that if the property doesn't define a DisplayName attribute we return the property name.

Answer 2

Try this:

var attribute =typeof(MyClass).GetProperty("Name").GetCustomAttributes(typeof(DisplayNameAttribute), true).Cast<DisplayNameAttribute>().Single();
string displayName = attribute.DisplayName; 

Hopefully It's help for you.