Eval C#表达式计算

时间:2022-11-25 15:56:10
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); 
                  }
              }
" ;
    }

}