计算字符串格式的表达式

新建一个类:

using System;
using System.CodeDom.Compiler;
using System.Reflection;
using System.Text;
using Microsoft.CSharp;   


namespace YYC.BLL
{
    /**////   <summary>   
    ///   计算表达式的类   
    ///   </summary>   
    public class CalculateExpression
    {
        /**////   <summary>   
        ///   接受一个string类型的表达式并计算结果,返回一个object对象,静态方法   
        ///   </summary>   
        ///   <param   name="expression"></param>   
        ///   <returns></returns>   
        public static object Calculate(string expression)
        {
            string className = "Calc";
            string methodName = "Run";
            expression = expression.Replace("/", "*1.0/");

            //   创建编译器实例。     
            CodeDomProvider complier = (new Microsoft.CSharp.CSharpCodeProvider());
            //   设置编译参数。     
            CompilerParameters paras = new CompilerParameters();
            paras.GenerateExecutable = false;
            paras.GenerateInMemory = true;

            //   创建动态代码。     
            StringBuilder classSource = new StringBuilder();
            classSource.Append("public   class   " + className + "\n");
            classSource.Append("{\n");
            classSource.Append("         public   object   " + methodName + "()\n");
            classSource.Append("         {\n");
            classSource.Append("                 return   " + expression + ";\n");
            classSource.Append("         }\n");
            classSource.Append("}");

            //   编译代码。     
            CompilerResults result = complier.CompileAssemblyFromSource(paras, classSource.ToString());

            //   获取编译后的程序集。     
            Assembly assembly = result.CompiledAssembly;

            //   动态调用方法。     
            object eval = assembly.CreateInstance(className);
            MethodInfo method = eval.GetType().GetMethod(methodName);
            object reobj = method.Invoke(eval, null);
            GC.Collect();
            return reobj;
        }
    }
}
//   调用:
    protected void Page_Load(object sender, EventArgs e)
    {  
        //string str = "(a+b)/c-d";  进行参数的转化
        string a = "2", b = "3", c = "4", d = "1";
        string str = "("+a.ToString()+"+"+b.ToString()+")"+"/"+c.ToString()+"-"+d.ToString();
        // string str = "(2+12)/4-1";   实际参数
      
        this.Response.Write("<script>alert('" + str + "');</script>");
        double result;
        result = (double)YYC.BLL.CalculateExpression.Calculate(str);
        this.Response.Write("<script>alert('" + result + "');</script>");
    }