C# Eval

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using System.CodeDom.Compiler;
using System.Reflection;

namespace Eval_Demo
{
    
/// <summary>
    
/// 动态求值
    
/// </summary>
    public class Evaluator
    {
        
/// <summary>
        
/// 计算结果,如果表达式出错则抛出异常
        
/// </summary>
        
/// <param name="statement">表达式,如"1+2+3+4"</param>
        
/// <returns>结果</returns>
        public static object Eval(string statement)
        {
            
return _evaluatorType.InvokeMember(
                        
"Eval",
                        BindingFlags.InvokeMethod,
                        
null,
                        _evaluator,
                        
new object[] { statement }
                     );
        }

        
static Evaluator()
        {
            
//构造JScript的编译驱动代码
            CodeDomProvider provider = CodeDomProvider.CreateProvider("JScript");

            CompilerParameters parameters;
            parameters 
= new CompilerParameters();
            parameters.GenerateInMemory 
= true;

            CompilerResults results;
            results 
= provider.CompileAssemblyFromSource(parameters, _jscriptSource);

            Assembly assembly 
= results.CompiledAssembly;
            _evaluatorType 
= assembly.GetType("Evaluator");

            _evaluator 
= Activator.CreateInstance(_evaluatorType);
        }

        
private static object _evaluator = null;
        
private static Type _evaluatorType = null;

        
/// <summary>
        
/// JScript代码
        
/// </summary>
        private static readonly string _jscriptSource =
            
@"class Evaluator
              {
                  public function Eval(expr : String) : String 
                  { 
                     return eval(expr); 
                  }
              }
";
    }
}


class Program
    {
        
static void Main(string[] args)
        {
            Console.WriteLine(Evaluator.Eval(
"1+2+3+4+5+6+7+8+9"));//45
            Console.WriteLine(Evaluator.Eval("((10-2)/2+1)*3"));//15
        }
    }
posted @ 2008-01-28 10:22  RobotTech  阅读(1984)  评论(1编辑  收藏  举报