.net使用自定義類屬性實例

 一般來說，在.net中可以使用Type.GetCustomAttributes獲取類上的自定義屬性，可以使用PropertyInfo.GetCustomAttributes獲取屬性信息上的自定義屬性。

 
下面以定義一個簡單數據庫表的映射實體類來說明相關的使用方法,基於自定義類屬性和自定義類中的屬性的自定義屬性，可以方便的進行類標記和類中屬性的標記
 
創建一個類的自定義屬性，用於標識數據庫中的表名稱，需要繼承自Attribute類：

 

代碼如下: [AttributeUsage(AttributeTargets.Class, Inherited = false, AllowMultiple = false)]
public sealed class TableAttribute : Attribute
{
        private readonly string _TableName = "";
        public TableAttribute(string tableName)
        {
            this._TableName = tableName;
        }
        public string TableName
        {
            get { return this._TableName; }
        }
}

 

創建一個屬性的自定義屬性,用於標識數據庫表中字段的名稱，需要繼承自Attribute類：

 

 代碼如下: [AttributeUsage(AttributeTargets.Property, Inherited = false, AllowMultiple = false)]
public class FieldAttribute : Attribute
{
        private readonly string _FieldName = "";    ///數據庫的字段名稱
        private System.Data.DbType _Type = System.Data.DbType.String;   ///數據庫的字段類型
 
        public FieldAttribute(string fieldName)
       {
              this._FieldName=fieldName;
       }
 
        public FieldAttribute(string fieldName,System.Data.DbType type)
       {
              this._FieldName=fieldName;
              this._Type=type;
       }
 
       public string FieldName
        {
            get { return this._FieldName; }
        }
 
        public System.Data.DbType Type
        {
             get{return this._Type;}
        }
}

 
創建一個數據實體基類：

 

 

代碼如下: public class BaseEntity
{
        public BaseEntity()
        {
        }
 
         /// <summary>
        /// 獲取表名稱
        /// </summary>
        /// <returns></returns>
        public string GetTableName()
        {
            Type type = this.GetType();
            object[] objs = type.GetCustomAttributes(typeof(TableAttribute), true);
            if (objs.Length <= 0)
            {
                throw new Exception("實體類沒有標識TableAttribute屬性");
            }
            else
            {
                object obj = objs[0];
                TableAttribute ta = (TableAttribute)obj;
                return ta.TableName;                            //獲取表名稱
            }
        }
        /// <summary>
        /// 獲取數據實體類上的FieldAttribute
        /// </summary>
        /// <param name="propertyName"></param>
        /// <returns></returns>
        public FieldAttribute GetFieldAttribute(string propertyName)
        {
            PropertyInfo field = this.GetType().GetProperty(propertyName);
            if (field == null)
            {
                throw new Exception("屬性名" + propertyName + "不存在");
            }
            object[] objs = field.GetCustomAttributes(typeof(FieldAttribute), true);
            if (objs.Length <= 0)
            {
                throw new Exception("類體屬性名" + propertyName + "沒有標識FieldAttribute屬性");
            }
            else
            {
                object obj = objs[0];
                FieldAttribute fieldAttribute=(FieldAttribute)obj;
                fieldAttribute.FieldValue=field.GetValue(this,null);
                return fieldAttribute;
            }
        }
}

 
創建數據實體：

 

 

代碼如下: [Table("Wincms_Dictionary")]            ///映射到數據庫的Wincms_Dictionary表
public class Wincms_Dictionary : BaseEntity
{
         private int _DictionaryId;
 
         public Wincms_Dictionary()
         {
         }
 
        [Field("DictionaryId",DbType.Int32)]                ///映射到數據庫的Wincms_Dictionary表中的字段
        public int DictionaryId
        {
            get { return this._DictionaryId; }
            set
            {
                this._DictionaryId = value;
            }
        }
}
 
///基於實體類獲取實體對應的表名稱和字段名稱
public class Test
{
 
       public static void main(string[] args)
        {
               Wincms_Dictionary dict=new Wincms_Dictionary();
               Console.WriteLine("表名稱："+GetTableName(dict));
               Console.WriteLine("字段名稱:"+GetFieldName(dict,"DictionaryId"));
               Console.Read();
        }
 
       ///獲取實體表名稱
       public  static string GetTableName(BaseEntity entity)
       {
                return entity.GetTableName();
       }
 
       ///獲取實體字段名稱
       public static string GetFieldName(BaseEntity entity,string propertyName)
       {
              FieldAttribute fieldAttribute=entity.GetFieldAttribute(propertyName);
              return fieldAttribute.FieldName;
       }
}

輸出結果為：

 

 

代碼如下: 表名稱：Wincms_Dictionary
字段名稱：DictionaryId