创建一个中间数据结构来存储所需的信息，并将其用于排序，然后生成输出：

stringList
    .GroupBy(x => x[0])
    .Select(g => (Length: g.Sum(x => x.Length), Char: g.Key))
    .OrderByDescending(t => t.Length)
    .ThenBy(t => t.Char)
    .Select(t => $"{t.Length}-{t.Char}");

你就快成功了。最简单的方法是用你关心的属性创建一个更复杂的对象，用这些属性进行排序，然后在输出中只保留你想要的内容。比如：

stringList
    .GroupBy(x => x[0])
    .Select(g => new {
        Len = g.Sum(x => x.Length),
        Char = g.Key,
        Val = $"{g.Sum(x => x.Length)}-{g.Key}"
    })
    .OrderByDescending(x => Len)
    .ThenBy(x => x.Char)
    .Select(x => x.Val);

您可以在GroupBy之后添加一个Select，将组转换为包含排序依据的匿名对象。然后，您可以使用OrderByDescending和ThenBy进行排序。之后，Select返回所需的格式化字符串：

stringList.GroupBy(x => x[0]) // assuming all strings are non-empty
    .Select(g => new {
        LengthSum = g.Sum(x => x.Length),
        FirstChar = g.Key
    })
    .OrderByDescending(x => x.LengthSum)
    .ThenBy(x => x.FirstChar)
    .Select(x => $"{x.LengthSum}-{x.FirstChar}");

或者，在带有let子句的查询语法中执行此操作，我发现这样更容易阅读：

var query = from str in stringList
    group str by str[0] into g
    let lengthSum = g.Sum(x => x.Length)
    let firstChar = g.Key
    orderby lengthSum descending, firstChar
    select $"{lengthSum}-{firstChar}";