采用表达式树(Expression Tree)对一个对象的属性进行“遍历”

实体类:

    public class Student          {              public int Id { get; set; }              public string Name { get; set; }              public string[] MultipleCareers { get; set; }            public Location Location { get; set; }          }           public class Location           {               public int Row { get; set; }               public int Col { get; set; }           }  

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Program.cs代码:

 class Program    {        private static void Main(string[] args)        {            object student = new Student            {                Id = 1,                Name = "zhang san",                MultipleCareers =new string[]{"教师","程序员","作家","画家"},                Location = new Location                {                    Row = 10,                    Col = 20                }            };            VisitProperties<Student>(student);        }        /// <summary>        ///     对未知类型的对象的属性进行递归访问        /// </summary>        /// <typeparam name="T"></typeparam>        /// <param name="obj"></param>        private static void VisitProperties<T>(object obj)        {            Type type = obj.GetType();            ParameterExpression paraExpression = Expression.Parameter(typeof (T), "object");            foreach (PropertyInfo prop in type.GetProperties())            {                Type propType = prop.PropertyType;                //判断是否为基本类型或String                  //访问方式的表达式树为：obj =>obj.Property                  if (propType.IsPrimitive || propType == typeof (String))                {                    VisitProperty<T>(obj, prop, paraExpression, paraExpression);                }                else                {                    //对于访问方式的表达式树为： obj=>obj.otherObj.Property。                      Console.WriteLine("not primitive property: " + prop.Name);                    Type otherType = prop.PropertyType;                    MemberExpression memberExpression = Expression.Property(paraExpression, prop);                    //访问obj.otherObj里的所有公有属性                      foreach (PropertyInfo otherProp in otherType.GetProperties())                    {                        VisitProperty<T>(obj, otherProp, memberExpression, paraExpression);                    }                }                Console.WriteLine("--------------------------------");            }        }        /// <summary>        ///     执行表达式树为： obj=>obj.Property 或 obj=>obj.otherObj.Property的计算        /// </summary>        /// <param name="instanceExpression">最终访问属性的obj对象的表达式树的表示</param>        /// <param name="parameterExpression">类型T的参数表达式树的表示</param>        private static void VisitProperty<T>(Object obj, PropertyInfo prop, Expression instanceExpression, ParameterExpression parameterExpression)        {            Console.WriteLine("property name: " + prop.Name);            MemberExpression memExpression = Expression.Property(instanceExpression, prop);            //实现类型转换，如将Id的int类型转为object类型，便于下面的通用性              Expression objectExpression = Expression.Convert(memExpression, typeof (object));            Expression<Func<T, object>> lambdaExpression = Expression.Lambda<Func<T, object>>(objectExpression,                parameterExpression);            //打印表达式树              Console.WriteLine("expression tree: " + lambdaExpression);            Func<T, object> func = lambdaExpression.Compile();            Console.WriteLine("value: " + func((T) obj)); //打印出得到的属性值          }    }

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运行结果如图: