Lambda表达式作为动态调度操作的参数 [英] Lambda expression as an argument to a dynamically dispatched operation

问题描述

被错误卡住:

Cannot use a lambda expression as an argument to a dynamically dispatched operation without first casting it to a delegate or expression tree type

对于一个简单的示例，让我们尝试使用实体框架从数据库中获取对象，而实际上不知道其类型:

For a simple example, let's try to get an object from database using entity framework without actually knowing its type:

private DbContext db;
private dynamic test(dynamic entity)
{
    return db.Set(entity.GetType()).First(x => x.Id == entity.Id);
}

我该如何进行这项工作?

How can I make this work?

推荐答案

使用泛型而不是dynamic:

private DbContext db;
private T test<T>(T entity)
    where T : BaseEntity
{
    return db.Set<T>().First(x => x.Id == entity.Id);
}

具有一个具有Id属性的BaseEntity，以确保给定的实体具有ID.

Have a BaseEntity that has an Id property, to ensure that the given entity has an Id.

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