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[ASP.net教程]定义通用的可通过lambda表达式树来获取属性信息


我们一般获取某个类型或对象的属性信息均采用以下几种方法:

一、通过类型来获取属性信息var p= typeof(People).GetProperty("Age");//获取指定属性var ps = typeof(People).GetProperties();//获取类型的所有属性二、通过实例来获取属性信息People people = new People();var pro = people.GetType().GetProperty("Age");var pros = people.GetType().GetProperties();

这两种方法都有其弊端,第一种与第二种方法,在获取单个属性信息时,都需要硬编码写入常量属性名称,这样在编译时并不会报错,只有在运行时才知道异常,第二种方法若只是需要获取属性的类型名称等基本信息,不需要属性的值,就不需要实例化类型。

鉴于以上原因,我定义了通用的可通过lambda表达式树来获取属性信息,使用方便,能解决上述问题,且有智能提示,若出现错误,编译时就能报出,方法定义代码如下:

    /// <summary>    /// 获取指定属性信息(非String类型存在装箱与拆箱)    /// </summary>    /// <typeparam name="T"></typeparam>    /// <param name="select"></param>    /// <returns></returns>    public static PropertyInfo GetPropertyInfo<T>(Expression<Func<T,dynamic>> select)     {      var body = select.Body;      if (body.NodeType == ExpressionType.Convert)      {        var o = (body as UnaryExpression).Operand;        return (o as MemberExpression).Member as PropertyInfo;      }      else if (body.NodeType == ExpressionType.MemberAccess)      {        return (body as MemberExpression).Member as PropertyInfo;      }      return null;    }    /// <summary>    /// 获取指定属性信息(需要明确指定属性类型,但不存在装箱与拆箱)    /// </summary>    /// <typeparam name="T"></typeparam>    /// <typeparam name="TR"></typeparam>    /// <param name="select"></param>    /// <returns></returns>    public static PropertyInfo GetPropertyInfo<T, TR>(Expression<Func<T, TR>> select)    {      var body = select.Body;      if (body.NodeType == ExpressionType.Convert)      {        var o = (body as UnaryExpression).Operand;        return (o as MemberExpression).Member as PropertyInfo;      }      else if (body.NodeType == ExpressionType.MemberAccess)      {        return (body as MemberExpression).Member as PropertyInfo;      }      return null;    }    /// <summary>    /// 获取类型的所有属性信息    /// </summary>    /// <typeparam name="T"></typeparam>    /// <param name="select"></param>    /// <returns></returns>    public static PropertyInfo[] GetPropertyInfos<T>(Expression<Func<T,dynamic>> select)    {      var body = select.Body;      if (body.NodeType == ExpressionType.Parameter)      {        return (body as ParameterExpression).Type.GetProperties();      }      else if(body.NodeType==ExpressionType.New)      {        return (body as NewExpression).Members.Select(m => m as PropertyInfo).ToArray();      }      return null;    }

使用很简单:

// People类型定义class People  {    public string Name    { get; set; }    public int Age    { get; set; }    public string Sex    { get; set; }    public bool IsBuyCar    { get; set; }    public DateTime? Birthday    { get; set; }  }//以下是使用方法:var p = GetPropertyInfo<People>(t => t.Age);//获取指定属性var ps1 = GetPropertyInfos<People>(t => t);//获取类型所有属性var ps2 = GetPropertyInfos<People>(t => new { t.Name, t.Age });//获取部份属性

  

注意dynamic类型也存在装箱与拆箱的问题,详见这篇博文:http://www.cnblogs.com/yank/p/4177619.html