c# - C# 中的 LINQ group by 和 order by

Question

我需要将我的城市列表按州分组并按城市排序。

我尝试了以下一项，但无法正确处理。将不胜感激任何帮助。

cities.GroupBy(g => g.state).Select(o => o.OrderBy(c => c.cityname));

Answer 1

试试下面的代码

cities.GroupBy(g => g.state)
.Select(o =>new { 
          State = o.Key,
         Cities = o.OrderBy(c => c.cityname).Tolist()})
.Tolist();

Answer 2

The ToLookup function may give you what you need.

cities.ToLookup(c => c.state, c => c.city);

This will create an IGrouping<string, string> where you can iterate through the Key values (states) and operate on a set of city values.

To sort it first, just do cities.OrderBy(c => c.state).ThenBy(c => c.city).

Answer 3

cits.OrderBy(d => d.cityname).GroupBy(d => d.state).SelectMany(g => g).ToList();

1 -cityname先排序。

2 - 然后根据 对它们进行分组state。由于您首先订购，因此仍然根据cityname属性对组进行订购。

3 - 转换为单个列表。否则，您将得到组列表。

应该管用。我还建议使用骆驼大小写表示法来命名变量。

Answer 4

先做orderby：

cities.OrderBy(c=>c.cityname).GroupBy (c => c.state);

您可能想要命令各州这样做。

cities.OrderBy(c=>c.cityname).GroupBy (c => c.state).OrderBy (g => g.Key);