Attributs personnalisés

Attributs personnalisés

Dans mon exemple je vais simuler un attribut personnalisé de Mapping comme le fait Linq To SQL

1 – Créer une classe pour cet attribut personnalisé

celle-ci doit hériter de System.Attribute

[AttributeUsage(AttributeTargets.Property,AllowMultiple=false)]

public class MappingAttribute : System.Attribute

    {

        private string _Storage;

        public string Storage

        {

            get { return _Storage; }

            set { _Storage = value; }

        }

        private string _Name;

        public string Name

        {

            get { return _Name; }

            set { _Name = value; }

        }

        private bool _isPrimaryKey;

        public bool IsPrimaryKey

        {

            get { return _isPrimaryKey; }

            set { _isPrimaryKey = value; }

        }

        private bool _CanBeNull;

        public bool CanBeNull

        {

            get { return _CanBeNull; }

            set { _CanBeNull = value; }

        }

        private string _DBType;

        public string DBType

        {

            get { return _DBType; }

            set { _DBType = value; }

        }

        public MappingAttribute()

        { }

        public MappingAttribute(string Storage, string Name, bool IsPrimaryKey, bool CanBeNull, string DBType)

        {

            this.Storage = Storage;

            this.Name = Name;

            this.IsPrimaryKey = IsPrimaryKey;

            this.CanBeNull = CanBeNull;

            this.DBType = DBType;

        }

2 – Utilisation de l’attribut personnalisé que je viens de créer

public class Contact

    {

        private string _ContactName;

        [MappingAttribute(Storage = "ContactName", Name = "Name", DBType = "CHAR(150)", IsPrimaryKey = false, CanBeNull = false)]

        public string ContactName

        {

            get { return _ContactName; }

            set { _ContactName = value; }

        }

        public Contact()

        { }

        public Contact(string ContactName)

        {

            this.ContactName = ContactName;

        }

    }

3 – Récupérer les informations grâce à la reflection durant l’exécution du programme

private void button1_Click(object sender, EventArgs e)

        {

            Contact oContact = new Contact("Romagny");

            MessageBox.Show(GetMappingAttributeOfProperty("ContactName").Name);

        }

        public MappingAttribute GetMappingAttributeOfProperty(string PropertyName)

        {

            MappingAttribute oMappingAttribute = null;

            System.Reflection.Assembly oAssembly = System.Reflection.Assembly.GetExecutingAssembly();

            foreach(Type oType in oAssembly.GetTypes())

            {

                if (oType.Name == "Contact")

                {

                    foreach (System.Reflection.PropertyInfo oPropertyInfo in oType.GetProperties())

                    {

                        if (oPropertyInfo.Name == PropertyName)

                        {

                            object[] CustomAttributes = oPropertyInfo.GetCustomAttributes(typeof(MappingAttribute), true);

                            oMappingAttribute = CustomAttributes[0] as MappingAttribute;

                        }

                    }

                }

            }

            return oMappingAttribute;

        } 

  

// OU plus rapide

 public MappingAttribute GetMappingAttributeOfProperty(string PropertyName)

        {

            System.Reflection.Assembly oAssembly = System.Reflection.Assembly.GetExecutingAssembly();

            return oAssembly.GetType("AttributsPersonnalises.Contact").GetProperty(PropertyName).GetCustomAttributes(typeof(MappingAttribute), true)[0] as MappingAttribute;

        }