linq重复行

Question

你能帮忙复制下面出现在linq表达式中的“for”语句吗？

List<RawData> rawList = [{ "address":"adr1","id":[11,12,13],"city":"NYC"},{"address":"adr2","id":[22,23],"city":"Boston"}, {"address":"adr3","id":[77],"city":"Chicago"}];

List<Data> list = new List<Data>();
foreach (var item in rawList)
{
    foreach (var id in item.idList)
    {
        Data d = new Data
        {
            id = id,
            address = item.address,
            city = item.city
        };
        list.Add(d);
    }
}

Answer 1

使用SelectMany方法在LINQ中展平：

var res = rawList
    .SelectMany(item => item.idList
        .Select(id => new Data {
            id = id,
            address = item.address,
            city = item.city
        })
    ).ToList();

一旦你理解了它的作用，其余部分就是不言自明的。