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.net使用自定義類屬性實(shí)例

 更新時(shí)間:2014年10月10日 09:54:19   投稿:shichen2014  
這篇文章主要介紹了.net使用自定義類屬性實(shí)例,詳細(xì)講述了自定義類屬性的原理及實(shí)現(xiàn)方法,需要的朋友可以參考下

一般來(lái)說(shuō),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(gè)簡(jiǎn)單數(shù)據(jù)庫(kù)表的映射實(shí)體類來(lái)說(shuō)明相關(guān)的使用方法,基于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(jìn)行類標(biāo)記和類中屬性的標(biāo)記
 
創(chuàng)建一個(gè)類的自定義屬性,用于標(biāo)識(shí)數(shù)據(jù)庫(kù)中的表名稱,需要繼承自Attribute類:

復(fù)制代碼 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(chuàng)建一個(gè)屬性的自定義屬性,用于標(biāo)識(shí)數(shù)據(jù)庫(kù)表中字段的名稱,需要繼承自Attribute類:

復(fù)制代碼 代碼如下:
[AttributeUsage(AttributeTargets.Property, Inherited = false, AllowMultiple = false)]
public class FieldAttribute : Attribute
{
        private readonly string _FieldName = "";    ///數(shù)據(jù)庫(kù)的字段名稱
        private System.Data.DbType _Type = System.Data.DbType.String;   ///數(shù)據(jù)庫(kù)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(chuàng)建一個(gè)數(shù)據(jù)實(shí)體基類:

復(fù)制代碼 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(shí)體類沒(méi)有標(biāo)識(shí)TableAttribute屬性");
            }
            else
            {
                object obj = objs[0];
                TableAttribute ta = (TableAttribute)obj;
                return ta.TableName;                            //獲取表名稱
            }
        }
        /// <summary>
        /// 獲取數(shù)據(jù)實(shí)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(méi)有標(biāo)識(shí)FieldAttribute屬性");
            }
            else
            {
                object obj = objs[0];
                FieldAttribute fieldAttribute=(FieldAttribute)obj;
                fieldAttribute.FieldValue=field.GetValue(this,null);
                return fieldAttribute;
            }
        }
}

 
創(chuàng)建數(shù)據(jù)實(shí)體:

復(fù)制代碼 代碼如下:
[Table("Wincms_Dictionary")]            ///映射到數(shù)據(jù)庫(kù)的Wincms_Dictionary表
public class Wincms_Dictionary : BaseEntity
{
         private int _DictionaryId;
 
         public Wincms_Dictionary()
         {
         }
 
        [Field("DictionaryId",DbType.Int32)]                ///映射到數(shù)據(jù)庫(kù)的Wincms_Dictionary表中的字段
        public int DictionaryId
        {
            get { return this._DictionaryId; }
            set
            {
                this._DictionaryId = value;
            }
        }
}
 
///基于實(shí)體類獲取實(shí)體對(duì)應(yīng)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(shí)體表名稱
       public  static string GetTableName(BaseEntity entity)
       {
                return entity.GetTableName();
       }
 
       ///獲取實(shí)體字段名稱
       public static string GetFieldName(BaseEntity entity,string propertyName)
       {
              FieldAttribute fieldAttribute=entity.GetFieldAttribute(propertyName);
              return fieldAttribute.FieldName;
       }
}

輸出結(jié)果為:

復(fù)制代碼 代碼如下:
表名稱:Wincms_Dictionary
字段名稱:DictionaryId

希望本文所述對(duì)大家的.net程序設(shè)計(jì)有所幫助。

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