.net使用自定义类属性
.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。
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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
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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
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??????? public FieldAttribute(string fieldName)
?????? {
????????????? this._FieldName=fieldName;
?????? }
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??????? public FieldAttribute(string fieldName,System.Data.DbType type)
?????? {
????????????? this._FieldName=fieldName;
????????????? this._Type=type;
?????? }
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?????? public string FieldName
??????? {
??????????? get { return this._FieldName; }
??????? }
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??????? public System.Data.DbType Type
??????? {
???????????? get{return this._Type;}
??????? }
???? }
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创建一个数据实体基类：
public class BaseEntity
{
??????? public BaseEntity()
??????? {
??????? }
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???????? /// <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;
??????????? }
??????? }
}
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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;
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???????? public Wincms_Dictionary()
???????? {
???????? }
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??????? [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;
??????????? }
??????? }
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}
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///基于实体类获取实体对应的表名称和字段名称
public class Test
{
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?????? 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();
??????? }
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?????? ///获取实体表名称
?????? public? static string GetTableName(BaseEntity entity)
?????? {
??????????????? return entity.GetTableName();
?????? }
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?????? ///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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