c#字符串中包含的運算符按正常計算 例如按四則運算等，類似公式計算，很好很強大

[csharp] 
/// <summary> 
/// 將字符串中的運算符按正常計算 例如按四則運算 
/// </summary> 
/// <param name="expression">標准表達式如 1+15*0.5-200</param> 
/// <returns>返回計算的值，可以為任意合法的數據類型</returns> 
protected static object MathCalculate(string expression) 
{ 
    object retvar = null; 
    Microsoft.CSharp.CSharpCodeProvider provider = new Microsoft.CSharp.CSharpCodeProvider(); 
    System.CodeDom.Compiler.CompilerParameters cp = new System.CodeDom.Compiler.CompilerParameters( 
    new string[] { @"System.dll" }); 
    StringBuilder builder = new StringBuilder("using System;class CalcExp{public static object Calc(){ return \"expression\";}}"); 
    builder.Replace("\"expression\"", expression); 
    string code = builder.ToString(); 
    System.CodeDom.Compiler.CompilerResults results; 
    results = provider.CompileAssemblyFromSource(cp, new string[] { code }); 
    if (results.Errors.HasErrors) 
    { 
        retvar = null; 
    } 
    else 
    { 
        System.Reflection.Assembly a = results.CompiledAssembly; 
        Type t = a.GetType("CalcExp"); 
        retvar = t.InvokeMember("Calc", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.InvokeMethod 
            , System.Type.DefaultBinder, null, null); 
    } 
    return retvar; 
}