Linq表達式的簡單應用

目標：比較類型相同的兩個對象，看看有哪些屬性值發生了變化

class static MyExtension

{

    //參數oldObject 原始對象， 參數newObject新對象

    //compareProperties 需要比較的屬性（t => t.Name, t => t.Id, ...）

    public static string GetModifyRemark<T>(thisT oldObject, T newObject,paramsExpression<Func<T, object>>[] compareProperties)
        {
            stringspliter = "";
            StringBuilder sb= newStringBuilder();
            foreach (var property in compareProperties)
            {
                if (property == null) continue;

                //將輸入的表達式轉換成成員表達式
                MemberExpression body = property.Body as MemberExpression;
                if (body == null)
                {

                    //如果表達式不是成員表達式，則轉換成一元表達式
                    UnaryExpression temp = property.Body asUnaryExpression;
                    if (temp != null)

                        //將一元表達式的Operand 轉換成成員表達式
                        body = temp.Operand as MemberExpression;
                }


                if(body == null)
                    throw new System.Exception(string.Format("Error Expression:{0}!", property));

                //根據屬性名獲取屬性信息對象，如果該屬性不可讀，則轉向下一循環
                PropertyInfo pi = typeof(T).GetProperty(body.Member.Name);
                if (pi.CanRead == false)
                    continue;

                //獲取兩個對象在指定屬性上的值
                object oldProperyValue = pi.GetValue(oldObject, null);
                object newProperyValue = pi.GetValue(newObject, null);
                if (Compare(oldProperyValue, newProperyValue) == false)
                {
                    sb.AppendFormat("{2}{3} from {0} to {1}", oldProperyValue, newProperyValue, spliter, body.Member.Name);
                    spliter = ", ";
                }
            }
            return sb.ToString();
        }


        private static bool Compare(object objA, object objB)
        {
            int result = 0;

            //判斷兩個對象是否可以直接比較
            if (objA is IComparable)
            {
                result = ((IComparable)objA).CompareTo(objB);
            }
            else
                result = objA.ToString().CompareTo(objB.ToString());

            return result == 0;
        }

}




class Student

{

        public stringName{get; set;}

        public int Age{get; set;}

        public string Sex{get; set;}


}




public class Program

{

     public static void Main()

     {

           Student s1 = new Student (){Name = "zs", Age = 11, Sex = "Male"};

           Student s2 = new Student (){Name = "zs", Age = 12, Sex = "FeMale"};




           string result = s1.GetModifyRemark(s2, s => s.Age, s => s.Sex);

           Console.WriteLine(result);

     }

}