有很多干净的方式来处理这个问题。如果你想第一个记录对应 ID 你可以说：

There are a lot of clean ways to handle this. If you want the first Record corresponding to id you can say:

Record record = data.Records.FirstOrDefault(r => r.Id == id);
if(record != null) {
    // record exists
}
else {
    // record does not exist
}

如果您只想知道如果这样的记录存在：

If you only want to know if such a Record exists:

return data.Records.Any(r => r.Id == id); // true if exists

如果你想的数有多少这样的记录存在：

If you want a count of how many such Record exists:

return data.Records.Count(r => r.Id == id);

如果你想要一个枚举（的IEnumerable＆LT;记录＆GT; ）的所有这样的记录：

If you want an enumeration (IEnumerable<Record>) of all such Record:

return data.Records.Where(r => r.Id == id);