.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:
[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
[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:
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
[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:
表名称:Wincms_Dictionary
字段名称:DictionaryId
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