字串計算運算式

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string str="4+4+2.1";

要的效果： double sum=4+4+2.1；

方案一：

動態計算運算式：

 1  public class Expression 2     { 3         object instance; 4         MethodInfo method; 5         /// <summary> 6         /// 表達試運算 7         /// </summary> 8         /// <param name="expression">表達試</param> 9         public Expression(string expression)10         {11             if (expression.IndexOf("return") < 0) expression = "return " + expression + ";";12             string className = "Expression";13             string methodName = "Compute";14             CompilerParameters p = new CompilerParameters();15             p.GenerateInMemory = true;16             CompilerResults cr = new CSharpCodeProvider().CompileAssemblyFromSource(p, string.17               Format("using System;sealed class {0}{{public double {1}(double x){{{2}}}}}",18               className, methodName, expression));19             if (cr.Errors.Count > 0)20             {21                 string msg = "Expression(\"" + expression + "\"): \n";22                 foreach (CompilerError err in cr.Errors) msg += err.ToString() + "\n";23                 throw new Exception(msg);24             }25             instance = cr.CompiledAssembly.CreateInstance(className);26             method = instance.GetType().GetMethod(methodName);27         }28         /// <summary>29         /// 處理資料30         /// </summary>31         /// <param name="x"></param>32         /// <returns>返回計算值</returns>33         public double Compute(double x)34         {35             return (double)method.Invoke(instance, new object[] { x });36         }

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方案二：

歡迎你們提供！