c# - 解析“DateTime.Now”？

Question

我需要翻译这样的字符串：

"DateTime.Now.AddDays(-7)"

转化为它们的等价表达式。

我只对 DateTime 类感兴趣。.Net 中是否有任何内置功能可以帮助我做到这一点，或者我只需要编写自己的小解析器？

Answer 1

您可以使用FLEE为您进行表达式解析。下面的代码在 Silverlight 中经过测试和工作（我相信在完整的 C# 中，创建表达式的语法可能略有不同，但无论如何它可能完全像这样工作）

ExpressionContext context = new ExpressionContext();

//Tell FLEE to expect a DateTime result; if the expression evaluates otherwise, 
//throws an ExpressionCompileException when compiling the expression
context.Options.ResultType = typeof(DateTime);

//Instruct FLEE to expose the `DateTime` static members and have 
//them accessible via "DateTime".
//This mimics the same exact C# syntax to access `DateTime.Now`
context.Imports.AddType(typeof(DateTime), "DateTime");

//Parse the expression, naturally the string would come from your data source
IDynamicExpression expression = ExpressionFactory.CreateDynamic("DateTime.Now.AddDays(-7)", context);

//I believe there's a syntax in full C# that lets you evaluate this 
//with a generic flag, but in this build, I only have it return type 
//`Object` so we cast (it does return a `DateTime` though)
DateTime date = (DateTime)expression.Evaluate();

Console.WriteLine(date); //January 25th (7 days ago for me!)