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); 

                  }

              }

"

;

    }

}