Eval C#表达式计算

Console.WriteLine(Evaluator.Eval("1+2+3+4+5+6+7+8+9"));//45

Console.WriteLine(Evaluator.Eval("(1+1)/2*3"));

Console.WriteLine(Evaluator.Eval("((10-2)/2+1)*3"));//15

 

 
  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); 
                  }
              } 
  " 
  ;
    }
 
 

}