如何获得主键

Question

I have a model

     public class Application : BaseModel, IApplication
     {
       [Key]
       public int ApplicationId { get; set; }

       public DateTime? Date { get; set; }

       public string ApplicationTypeId { get; set; }

       public List<AlternateSigningAuthority> AlternateSigningAuthorities { get; set; }

       public List<Land> Lands { get; set; }

     }

And another model

     public class Land : BaseModel, IEquatable<Land>/*, ILand*/
    {

       [Key]
        public int LandId { get; set; }

       [ForeignKey("ApplicationId")]
        public int ApplicationId { get; set; }

        public int Unit { get; set; }
    }

Similary I have a model for AlternateSigningAuthority. I want to get Primary Keys of these models.

I have code which works for Application

           var type = typeof(Application);
           var properties = type.GetProperties();

           var property = properties
                .FirstOrDefault(p => p.GetCustomAttributes(false)
                    .Any(a => a.GetType() == typeof(KeyAttribute)));

            if (property != null)
            {
                string msg = "The Primary Key for the {0} class is the {1} property";
                Console.WriteLine(msg, type.Name, property.Name);
            }

AS soon as I add

    foreach (var prop in properties)
        {
            var attributes = property.GetCustomAttributes(false);
            foreach (var attribute in attributes)
            {
                if (attribute.GetType() == typeof(KeyAttribute))
                {
                    string msg = "The Primary Key for the {0} class is the {1} property";
                    Console.WriteLine(msg, type.Name, attribute.ToString());
                }
            }

I dont get Primary keys. I want to use Application Model to get keys for other models.

Answer 1

You just need to call Attribute.GetCustomAttribute

AddressViewModel viewModelInstance=new AddressViewModel();
        PropertyInfo[] properties = viewModelInstance.GetType().GetProperties();

        foreach (PropertyInfo property in properties)
        {
            var attribute = Attribute.GetCustomAttribute(property, typeof(KeyAttribute))
                as KeyAttribute;

            if (attribute != null) // This property has a KeyAttribute
            {
                // Do something, to read from the property:
                object val = property.GetValue(viewModelInstance);
            }
        }

I referred this link Get [key] property from ViewModel

Answer 2

public void WriteKeyProperty(Type classType)
{
    var properties = classType.GetProperties();
    foreach (var property in properties)
    {
        var keyAttribute = property.GetCustomAttribute(typeof(KeyAttribute));
        if (keyAttribute == null) continue;
        const string msg = "The Primary Key for the {0} class is the {1} property";
        Console.WriteLine(msg, classType.Name, property.Name);
    }
}

And the call is

WriteKeyProperty(typeof(Application));
WriteKeyProperty(typeof(Land));

Answer 3

No sure what u are trying to do. your first code:

var property = properties
                .FirstOrDefault(p => p.GetCustomAttributes(false)
                    .Any(a => a.GetType() == typeof(KeyAttribute)));

the property is PropertyInfo, therefore it gives you the name of the primary key. The a => a.GetType() == typeof(KeyAttribute) return the uniquely identifier of the class. So it is returning ApplicationId.

Your second code is not working because you are returning name of the CustomAttribute which is a object type.

I think your first code should work for all 3 classes.