排序列表并在排序后将特定元素保留在列表的末尾

Question

我有一个包含字符串的列表"Others".我得到这个列表下拉.我按字母顺序排序这个列表.但我"Others"总是需要在列表的末尾.我不想在排序后添加这个元素,这是一个解决方案.有没有其他方法可以像使用.Sort()方法的自定义比较器一样.我试过下面但没有解决方案.

 public class EOComparer : IComparer<string>
    {
        public int Compare(string x, string y)
        {
            if (x == null)
            {
                if (y == null)
                {
                    // If x is null and y is null, they're
                    // equal. 
                    return 0;
                }
                else
                {
                    // If x is null and y is not null, y
                    // is greater. 
                    return -1;
                }
            }
            else
            {
                // If x is not null...
                //
                if (y == null)
                // ...and y is null, x is greater.
                {
                    return 1;
                }
                else
                {
                    if (x.ToLower().Contains("other"))
                    {
                        return -1;
                    }
                    else
                    {
                        // If the strings are of equal length,
                        // sort them with ordinary string comparison.
                        //
                        return x.CompareTo(y);
                    }
                }
            }
        }

并将其称为:

EOComparer c = new EOComparer();
a.Sort((x, y) => c.Compare(x.OptionValue, y.OptionValue));
             return a;

如果有可能请帮忙.

Answer 1

使用这个逻辑

List<string> l = new List<string>{ "z", "y", "x", "other", "b", "a", "c" };
var result = l.OrderBy(i => i == "other").ThenBy(i => i).ToList();
result.ForEach(Console.WriteLine);

输出:

abcxyz其他

如果你想other成为列表的顶部

var result = l.OrderBy(i => i != "other").ThenBy(i => i).ToList();

输出:

其他abcxyz

Answer 2

这是一个很好的答案,但我想我会修复你的比较器:

测试:

[TestCase(new string[0], new string[0])]
[TestCase(new[] { "a" }, new[] { "a" })]
[TestCase(new[] { "a", "b" }, new[] { "a", "b" })]
[TestCase(new[] { "b", "a" }, new[] { "a", "b" })]
[TestCase(new[] {"others"}, new[] {"others"})]
[TestCase(new[] {"a", "others"}, new[] {"a", "others"})]
[TestCase(new[] {"others", "a"}, new[] {"a", "others"})]
[TestCase(new[] {"others", "x"}, new[] {"x", "others"})]
[TestCase(new[] {"Others", "x"}, new[] {"x", "Others"})]
[TestCase(new[] { "othersz", "others" }, new[] { "othersz", "others" })]
[TestCase(new[] {"z", "y", "x", "others", "b", "a", "c"},
          new[] {"a", "b", "c", "x", "y", "z", "others"})]
public void CanSortWithOthersAtEnd(string[] input, string[] expectedSorted)
{
    var a = new List<string>(input);
    var c = new EOComparer();
    a.Sort(c.Compare);
    CollectionAssert.AreEqual(expectedSorted, a);
}

比较器:

public sealed class EOComparer : IComparer<string>
{
    public int Compare(string x, string y)
    {
        if (IsOthers(x)) return 1;
        if (IsOthers(y)) return -1;
        return string.Compare(x, y, StringComparison.Ordinal);
    }

    private static bool IsOthers(string str)
    {
        return string.Compare(str, "others", StringComparison.OrdinalIgnoreCase) == 0;
    }
}

注意我的使用如何string.Compare避免所有== null检查.以及如何StringComparison.OrdinalIgnoreCase避免.ToLower()并因此避免创建字符串的副本.