解析" DateTime.Now"？ [英] Parsing "DateTime.Now"?

问题描述

我需要这样的翻译字符串：

I need to translate strings like this:

"DateTime.Now.AddDays(-7)"

到他们的等值表达式。

into their equivalent expressions.

我只DateTime类感兴趣。有什么内置的.Net那会帮助我做到这一点，或者我只需要编写自己的小解析器？

I'm only interested in the DateTime class. Is there anything built into .Net that'll help me do this, or do I just need to write my own little parser?

推荐答案

您可以使用 FLEE 做表达式分析为您服务。下面的代码进行测试，并在Silverlight中工作（我相信完整的C＃，它可能围绕创建表达式的语法稍有不同，但也可能正是这样的工作反正）

You can employ FLEE to do the expression parsing for you. The below code is tested and working in Silverlight (I believe in full C#, it may have a slightly different syntax around creating the expression, but it might work exactly like this anyway)

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!)

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