C＃如何返回null或模型

Question

我有Store Model，如果我的模型为null，我想返回null。

public Store Details() => db.Store.Single(s => s.Id == 1);

此查询有时会返回一个值，有时会返回null。如何指定返回类型以包含两者？

Answer 1

尝试使用

public Store Details() => db.Store.FirstOrDefault(s => s.Id == 1);

Answer 2

使用 SingleOrDefault 而不是FirstOrDefault，因为如果找到多个，则抛出异常

// throws an exception if there's more than one entity that fits the filter part. 
public Store Details() => db.Store.SingleOrDefault(s => s.Id == 1);

// doesn't throw if there's more than one entity that fits the filter part
public Store Details() => db.Store.FirstOrDefault(s => s.Id == 1);