请教如何分析表达式树

Question

MSDN官方示例：

 

// Add the following using directive to your code file:
// using System.Linq.Expressions;
// Create an expression tree.
Expression<Func<int, bool>> exprTree = num => num < 5;
// Decompose the expression tree.
ParameterExpression param = (ParameterExpression)exprTree.Parameters[0];
BinaryExpression operation = (BinaryExpression)exprTree.Body;
ParameterExpression left = (ParameterExpression)operation.Left;
ConstantExpression right = (ConstantExpression)operation.Right;
Console.WriteLine("Decomposed expression: {0} => {1} {2} {3}",
                  param.Name, left.Name, operation.NodeType, right.Value);
// This code produces the following output:
// Decomposed expression: num => num LessThan 5 

但现在的代码却运行不了，请高手指点：

 

 

public class Test
    {
        public void ExpressionTest()
        {
            T t=new T(){ID=1,Name="abc"};
            Expression<Func<T, bool>> exprTree = o => o.ID == t.ID;
            ParameterExpression param = (ParameterExpression)exprTree
                                                             .Parameters[0];
            BinaryExpression operation = (BinaryExpression)exprTree.Body;
            MemberExpression left = (MemberExpression)operation.Left;
            MemberExpression right = 
                             (MemberExpression)operation.Right;//这里出错

            Console.WriteLine("Decomposed expression:{0}=>{1}{2}{3}",
                param.Name,left.Member.Name,operation.NodeType,right.Value);

        }
    }
    public class T
    {
        public int ID { get; set; }
        public string Name { get; set; }
    }

 

MemberExpression right = (MemberExpression)operation.Right;//这一句想得到表达式右边的1，
但程序总是出错，请高手指点