创建一个表达式来; Func键<，>>使用反射 [英] Create an Expression<Func<,>> using reflection

问题描述

使用起订量来创建一个数据集的嘲笑林。

Im using Moq to create mocks of a data set.

我创建了一个小帮手类，允许我在内存中存储有一个，而不是数据库的那做单元测试轻而易举。这样我可以添加和删除我的模拟数据组项目，这让我来测试我的插入和删除服务呼叫。

I have created a little helper class that allows me to have an in memory storage instead of a database that makes unit testing a breeze. That way I can add and remove items from my mock data set, this allows me to test my insert and delete service calls.

在模拟的设置我有一个线，看起来像以下

During the setup of the mock I have a line that looks like the following

this.Setup(i => i.AcademicCycles).Returns(mockStore.GetList<AcademicCycle>());

我假装有很多的属性，所以我想执行使用反射此设置步骤。我已成功地在返回的过程中通过反射工作的一部分，但我被困在拉姆达方法设置。

My mock has a lot of properties so I would like to perform this setup step using reflection. I have managed to the Returns part of the process working via reflection but I am stuck on the lambda method to Setup.

设置需要一个

表达式来; Func键< GoalsModelUnitOfWork，IQueryable的< AcademicCycle>>> 对应于 I => i.AcademicCycles

和我想动态地创建这一点。使用反射我有以下几点：

and I would like to create this dynamically. Using reflection I have the following:

属性的名称：AcademicCycles

The name of the property: "AcademicCycles"

键入的IQueryable< AcademicCycle>

键入 AcademicCycle

我也有 I 中拉姆达声明这是实例的 GoalsModelUnitOfWork

I also have the instance of the i in the lambda statement which is a GoalsModelUnitOfWork

推荐答案

中的代码创建表达式动态会是这样：

The code to create the expression dynamically would be like this:

ParameterExpression parameter = Expression.Parameter(typeof (GoalsModelUnitOfWork), "i");
MemberExpression property = Expression.Property(parameter, "AcademicCycles");

var queryableType = typeof (IQueryable<>).MakeGenericType(typeof (AcademicCycle));
var delegateType = typeof (Func<,>).MakeGenericType(typeof (GoalsModelUnitOfWork), queryableType);

var yourExpression = Expression.Lambda(delegateType, property, parameter);

结果将有需要的类型，但问题是，返回类型 Expression.Lambda（）是 LambdaExpression ，你不能到表达式来; Func键< ;. ..>> 将它传递作为参数传递给你的设置功能，因为你不知道的函数功能泛型类型参数。所以，你必须调用设置方法，通过反射太：

The result will have the desired type, but the problem is that the return type of Expression.Lambda() is LambdaExpression and you can't perform a type cast to Expression<Func<...>> to pass it as parameter to your setup function because you don't know the generic type parameters for the Func. So you have to invoke the Setup method by reflection, too:

this.GetType().GetMethod("Setup", yourExpression.GetType()).Invoke(this, yourExpression);

这篇关于创建一个表达式来; Func键&LT;，&GT;&GT;使用反射的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！