.net使用自定义类属性实例

一般来说,在.net中可以使用Type.GetCustomAttributes获取类上的自定义属性,可以使用PropertyInfo.GetCustomAttributes获取属性信息上的自定义属性。
 
下面以定义一个简单数据库表的映射实体类来说明相关的使用方法,基于自定义类属性和自定义类中的属性的自定义属性,可以方便的进行类标记和类中属性的标记
 
创建一个类的自定义属性,用于标识数据库中的表名称,需要继承自Attribute类:

代码如下:

[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; }

        }

}

创建一个属性的自定义属性,用于标识数据库表中字段的名称,需要继承自Attribute类:

代码如下:

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

public class FieldAttribute : Attribute

{

        private readonly string _FieldName = "";    ///数据库的字段名称

        private System.Data.DbType _Type = System.Data.DbType.String;   ///数据库的字段类型

 

        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;}

        }

}

 
创建一个数据实体基类:

代码如下:

public class BaseEntity

{

        public BaseEntity()

        {

        }

 

         /// <summary>

        /// 获取表名称

        /// </summary>

        /// <returns></returns>

        public string GetTableName()

        {

            Type type = this.GetType();

            object[] objs = type.GetCustomAttributes(typeof(TableAttribute), true);

            if (objs.Length <= 0)

            {

                throw new Exception("实体类没有标识TableAttribute属性");

            }

            else

            {

                object obj = objs[0];

                TableAttribute ta = (TableAttribute)obj;

                return ta.TableName;                            //获取表名称

            }

        }

        /// <summary>

        /// 获取数据实体类上的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("属性名" + propertyName + "不存在");

            }

            object[] objs = field.GetCustomAttributes(typeof(FieldAttribute), true);

            if (objs.Length <= 0)

            {

                throw new Exception("类体属性名" + propertyName + "没有标识FieldAttribute属性");

            }

            else

            {

                object obj = objs[0];

                FieldAttribute fieldAttribute=(FieldAttribute)obj;

                fieldAttribute.FieldValue=field.GetValue(this,null);

                return fieldAttribute;

            }

        }

}

 
创建数据实体:

代码如下:

[Table("Wincms_Dictionary")]            ///映射到数据库的Wincms_Dictionary表

public class Wincms_Dictionary : BaseEntity

{

         private int _DictionaryId;

 

         public Wincms_Dictionary()

         {

         }

 

        [Field("DictionaryId",DbType.Int32)]                ///映射到数据库的Wincms_Dictionary表中的字段

        public int DictionaryId

        {

            get { return this._DictionaryId; }

            set

            {

                this._DictionaryId = value;

            }

        }

}

 

///基于实体类获取实体对应的表名称和字段名称

public class Test

{

 

       public static void main(string[] args)

        {

               Wincms_Dictionary dict=new Wincms_Dictionary();

               Console.WriteLine("表名称:"+GetTableName(dict));

               Console.WriteLine("字段名称:"+GetFieldName(dict,"DictionaryId"));

               Console.Read();

        }

 

       ///获取实体表名称

       public  static string GetTableName(BaseEntity entity)

       {

                return entity.GetTableName();

       }

 

       ///获取实体字段名称

       public static string GetFieldName(BaseEntity entity,string propertyName)

       {

              FieldAttribute fieldAttribute=entity.GetFieldAttribute(propertyName);

              return fieldAttribute.FieldName;

       }

}

输出结果为:

代码如下:

表名称:Wincms_Dictionary

字段名称:DictionaryId

希望本文所述对大家的.net程序设计有所帮助。

相关推荐