C#动态执行公式运算

主要利用反射和动态编译。

示例代码：

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

namespace ConsoleApp6
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            Expression e = new Expression("x+5*9/3.2+6");
            Console.WriteLine(e.Compute(10));
            Console.Read();
        }
    }

    public class Expression
    {
        private object instance;
        private MethodInfo method;

        /// <summary>
        /// 表达试运算
        /// </summary>
        /// <param name="expression">表达试</param>
        public Expression(string expression)
        {
            if (expression.IndexOf("return") < 0)
            {
                expression = "return " + expression + ";";
            }

            string className = "Expression";
            string methodName = "Compute";
            CompilerParameters p = new CompilerParameters();
            p.GenerateInMemory = true;
            var source = string.Format("using System;sealed class {0}{{public double {1}(double x){{{2}}}}}", className, methodName, expression);
            CompilerResults cr = new CSharpCodeProvider().CompileAssemblyFromSource(p, source);
            if (cr.Errors.Count > 0)
            {
                string msg = "Expression(\"" + expression + "\"): \n";
                foreach (CompilerError err in cr.Errors)
                {
                    msg += err.ToString() + "\n";
                }
                throw new Exception(msg);
            }
            instance = cr.CompiledAssembly.CreateInstance(className);
            method = instance.GetType().GetMethod(methodName);
        }

        /// <summary>
        /// 处理数据
        /// </summary>
        /// <param name="x"></param>
        /// <returns>返回计算值</returns>
        public double Compute(double x)
        {
            return (double)method.Invoke(instance, new object[] { x });
        }
    }
}