转换表达式来; T，BOOL>为String [英] Converting Expression<T, bool> to String

问题描述

我需要一种方法来重新在未来的某个时候动态生成的报告。长话短说，我需要一个特定的LINQ查询（每个报告不同）存储到数据库中，然后执行动态的LINQ以后查询。

I need a way to recreate dynamically generated reports at some point in the future. Long story short, I need to store a specific linq query (different for each report) into database and then execute the query with dynamic Linq later on.

这是所有的好，但我不能找到一种方法来表达转换为字符串

This is all good, but I can't find a way to convert expression to string.

如：

Expression<Func<Product, bool>> exp = (x) => (x.Id > 5 && x.Warranty != false);

应该变成：

should become:

"Product.Id > 5 && Product.Warranty != false"

有没有办法做到这一点？

Is there a way to do that?

推荐答案

这可能不是最好/最有效的方法，但它< 。EM>确实的作品

This may not be the best/most efficient method, but it does work.

Expression<Func<Product, bool>> exp = (x) => (x.Id > 5 && x.Warranty != false);

string expBody = ((LambdaExpression)exp).Body.ToString(); 
// Gives: ((x.Id > 5) AndAlso (x.Warranty != False))

var paramName = exp.Parameters[0].Name;
var paramTypeName = exp.Parameters[0].Type.Name;

// You could easily add "OrElse" and others...
expBody = expBody.Replace(paramName + ".", paramTypeName + ".")
                 .Replace("AndAlso", "&&");


Console.WriteLine(expBody);
// Output: ((Product.Id > 5) && (Product.Warranty != False))

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