Question

I am trying to create a view model for editing which contains some slightly different fields then the main model, however it appears when trying to render a view for this view model it throws and exception because some properties are missing that are specified in the MetadataType.

Code:

[MetadataType(typeof(IAdministrator))]
    public partial class Administrator : IAdministrator
    {
        public string Name { get { return String.Format("{0} {1}", FirstName, LastName); } }
    }

    [MetadataType(typeof(IAdministrator))]
    public class AdministratorEdit
    {
        public int AdministratorID { get; set; }

        public string EmailAddress { get; set; }

        public string FirstName { get; set; }

        public string LastName { get; set; }

        [DisplayName("New Password")]
        [DataType(DataType.Password)]
        [StringLength(12, MinimumLength = 8)]
        public string NewPassword { get; set; }

        [DisplayName("Re-New Password")]
        [DataType(DataType.Password)]
        [StringLength(12, MinimumLength = 8)]
        public string ReNewPassword { get; set; }
    }

    public interface IAdministrator
    {
        [Required]
        [DisplayName("Email Address")]
        [DataType(DataType.EmailAddress)]
        [RegularExpression(@"^(([\w-]+\.)+[\w-]+|([a-zA-Z]{1}|[\w-]{2,}))@((([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])){1}|([a-zA-Z]+[\w-]+\.)+[a-zA-Z]{2,4})$")]
        [StringLength(320)]
        string EmailAddress { get; set; }

        [Required]
        [DisplayName("Password")]
        [DataType(DataType.Password)]
        [StringLength(12, MinimumLength = 8)]
        string Password { get; set; }

        [Required]
        [DisplayName("First Name")]
        [DataType(DataType.Text)]
        [StringLength(25)]
        string FirstName { get; set; }

        [Required]
        [DisplayName("Last Name")]
        [DataType(DataType.Text)]
        [StringLength(25)]
        string LastName { get; set; }

        [DisplayName("Date Created")]
        [DataType(DataType.Date)]
        DateTime Date { get; set; }
    }

This is the exception that I get from the view which uses the AdministratorEdit model:
The associated metadata type for type ‘….Models.AdministratorEdit’ contains the following unknown properties or fields: Password, Date. Please make sure that the names of these members match the names of the properties on the main type.

Can someone please sugest another method of creating a view model without having to specify another MetadataType or just a quick fix for this exception?

Answer 1

From your IAdminstrator interface you could extract a base class (interface), the base interface would just have the edit fields (IAdministratorEdit) and IAdministrator would remain with all fields, as it would inherit from the IAdministratorEdit.

public interface IAdministrator : IAdministratorEdit 

and then just use the IAdministratorEdit interface on your ViewModel. That way you only have to define the constraints in you metadata once.