AssociationAttribute.cs

using System.Collections.Generic;

namespace System.ComponentModel.DataAnnotations {
    /// <summary>
    /// Used to mark an Entity member as an association
    /// </summary>
    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
    public sealed class AssociationAttribute : Attribute {
        private string name;
        private string thisKey;
        private string otherKey;
        private bool isForeignKey;

        /// <summary>
        /// Full form of constructor
        /// </summary>
        /// <param name="name">The name of the association. For bi-directional associations, the name must
        /// be the same on both sides of the association</param>
        /// <param name="thisKey">Comma separated list of the property names of the key values
        /// on this side of the association</param>
        /// <param name="otherKey">Comma separated list of the property names of the key values
        /// on the other side of the association</param>
        public AssociationAttribute(string name, string thisKey, string otherKey) {
            this.name = name;
            this.thisKey = thisKey;
            this.otherKey = otherKey;
        }

        /// <summary>
        /// Gets the name of the association. For bi-directional associations, the name must
        /// be the same on both sides of the association
        /// </summary>
        public string Name {
            get { return this.name; }
        }

        /// <summary>
        /// Gets a comma separated list of the property names of the key values
        /// on this side of the association
        /// </summary>
        public string ThisKey {
            get {
                return this.thisKey;
            }
        }

        /// <summary>
        /// Gets a comma separated list of the property names of the key values
        /// on the other side of the association
        /// </summary>
        public string OtherKey {
            get {
                return this.otherKey;
            }
        }

        /// <summary>
        /// Gets or sets a value indicating whether this association member represents the foreign key
        /// side of an association
        /// </summary>
        public bool IsForeignKey {
            get {
                return this.isForeignKey;
            }
            set {
                this.isForeignKey = value;
            }
        }

        /// <summary>
        /// Gets the collection of individual key members specified in the ThisKey string.
        /// </summary>
        public IEnumerable<string> ThisKeyMembers {
            get {
                return GetKeyMembers(this.ThisKey);
            }
        }

        /// <summary>
        /// Gets the collection of individual key members specified in the OtherKey string.
        /// </summary>
        public IEnumerable<string> OtherKeyMembers {
            get {
                return GetKeyMembers(this.OtherKey);
            }
        }

        /// <summary>
        /// Parses the comma delimited key specified
        /// </summary>
        /// <param name="key">The key to parse</param>
        /// <returns>Array of individual key members</returns>
        private static string[] GetKeyMembers(string key) {
            return key.Replace(" ", string.Empty).Split(',');
        }
    }
}