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        .net使用自定義類屬性實例

        字號:


            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(shù)據(jù)庫表的映射實體類來說明相關(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)建一個類的自定義屬性,用于標(biāo)識數(shù)據(jù)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(chuàng)建一個屬性的自定義屬性,用于標(biāo)識數(shù)據(jù)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(shù)據(jù)庫的字段名稱
            private System.Data.DbType _Type = System.Data.DbType.String; ///數(shù)據(jù)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(chuàng)建一個數(shù)據(jù)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(biāo)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(shù)據(jù)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(biāo)識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)實體:
            代碼如下:
            [Table("Wincms_Dictionary")] ///映射到數(shù)據(jù)庫的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)庫的Wincms_Dictionary表中的字段
            public int DictionaryId
            {
            get { return this._DictionaryId; }
            set
            {
            this._DictionaryId = value;
            }
            }
            }
            ///基于實體類獲取實體對應(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(jié)果為:
            代碼如下:
            表名稱:Wincms_Dictionary
            字段名稱:DictionaryId