//  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

     // 实体类

     public   class  T

    {

         public   int  ID {  get ;  set ; }

         public   string  Name {  get ;  set ; }

    }

     // 解析表达式树类

     public   class  Test

    {

         public   void  ExpressionTest(Expression < Func < T,  bool >>  exprTree)

        {

            ParameterExpression param  =  (ParameterExpression)exprTree.Parameters[ 0 ];

            BinaryExpression operation  =  (BinaryExpression)exprTree.Body;

            MemberExpression left  =  (MemberExpression)operation.Left;

            MemberExpression right  =  (MemberExpression)operation.Right;

            var result = Expression.Lambda(right).Compile().DynamicInvoke();

            Console.WriteLine( " Decomposed expression:{0}=>{1} {2} {3} " ,

                param.Name,left.Member.Name,operation.NodeType,result.ToString());

        }

    }

     // 调用

     public   class  Program

    {

         static   void  Main( string [] args)

        {

            Test test  =   new  Test();

            T t  =   new  T() { ID  =   1 , Name  =   " abc "  };

            test.ExpressionTest(o  =>  o.ID  ==  t.ID);

            test.ExpressionTest(o  =>  o.Name  ==  t.Name);            

            Console.Read();

        }

    }