c#中动态输入和计算 代数表达式

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Collections;

using System.ComponentModel;

using System.CodeDom;

using System.CodeDom.Compiler;

using Microsoft.JScript;

using System.Reflection;

下面是一个完整的类，代码已经测试过

/// <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 }

);

}

/// <summary>

///

/// </summary>

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);

}

}";

}

调用很简单：Evaluator.Eval( "4*9+8" ) 返回的object 对象转化为数字就是计算的结果