将Linq表达式作为字符串传递? [英] Passing a Linq expression as a string?

问题描述

以下代码可以正常工作

        using (var ctx = new MyEntities())
        {
            var devices = ctx.Devices
               .Where(x=> x.Device == "TEST")
               .ToList();
            return devices;
        }

我想做的就是传递"Where"子句中的表达式.我看到它可以带一个字符串，但以下内容会引发错误:

What I would like to do is to pass in the expression that goes in the "Where" clause. I see that it can take a string but the following throws an error:

        String expression = "x=> x.Device == \"TEST\"" ;

        using (var ctx = new MyEntities())
        {
            var devices = ctx.Devices
               .Where(expression)
               .ToList();
            return devices;
        }

运行时错误消息为查询语法无效.近期术语>"，第6行，第4列."；传递最初源自字符串的表达式的最佳方法是什么?

The error message at runtime is "The query syntax is not valid. Near term '>', line 6, column 4."; What would be the best way to pass in an expression that is initially derived from a string?

推荐答案

您必须手动构建表达式.

You have to build the Expression manually.

IIRC，LINQ101示例中有一个DynamicExpressions库可以为您完成此操作.

IIRC, there is a DynamicExpressions library in the LINQ101 samples that can do this for you.

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