根据组内的值对WPF DataGrid进行排序

Question

我有一个由数据库查询填充的WPF DataGrid。初始结果在SQL中进行分组和排序：

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我希望我的用户能够根据任意的列进行排序，但是简单地按"Value“排序就会混淆这些组。我希望组保持分组，同时按指定的列进行排序。

例如，按列"Value“进行排序(升序)，应该按照每个组内的最小”值“对组进行排序。其结果应该是：

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我已经有了一个排序处理程序，我怀疑Linq在这里可能很有用，但是我似乎找不到一种方法来对值和GroupName进行排序。

Answer 1

这是一个很小的例子，如何按需要分组，您可以更改它，您的列表来自db，您可以像我一样做同样的事情，不要忘记IComparable。

static void Main(string[] args)
    {
        List<MyClass> inputlist = new List<MyClass>();
        inputlist.Add(new MyClass { GroupName = "A", Value = 10 });
        inputlist.Add(new MyClass { GroupName = "A", Value = 15 });
        inputlist.Add(new MyClass { GroupName = "A", Value = 20 });
        inputlist.Add(new MyClass { GroupName = "B", Value = 1 });
        inputlist.Add(new MyClass { GroupName = "B", Value = 10 });
        inputlist.Add(new MyClass { GroupName = "B", Value = 15 });
        inputlist.Add(new MyClass { GroupName = "C", Value = 5 });
        inputlist.Add(new MyClass { GroupName = "C", Value = 10 });
        inputlist.Add(new MyClass { GroupName = "C", Value = 15 });

        List<MyClass> outputlist = new List<MyClass>();

        foreach (var item in 
                inputlist.GroupBy(x => x.GroupName).Select(x => new MyClass
                {
                    GroupName = x.First().GroupName,
                    Value = x.Min().Value
                }).ToList().OrderBy(x => x.Value))
        {
            outputlist.AddRange(inputlist.Where(x => x.GroupName == item.GroupName));
        }

        foreach (var item in outputlist)
        {
            Console.WriteLine(item.GroupName + " " + item.Value);
        }
        Console.ReadLine();
    }
}

public class MyClass : IComparable
{
    public string GroupName { get; set; }
    public int Value { get; set; }

    public int CompareTo(object value)
    {
        int val = (int)Value;
        if (this.Value > val) return -1;
        if (this.Value == val) return 0;
        return 1;
    }

}

Answer 2

您确实需要以以下方式实现排序处理程序(请参阅代码中的注释)：

private void OnSorting(object sender, DataGridSortingEventArgs e) {
    if (e.Column.SortMemberPath == "Value") {
        // get view
        var source = (ListCollectionView) CollectionViewSource.GetDefaultView(this.Items);
        // manually change sort direction to the next value
        // so null > ascending > descending > back to null
        var sort = e.Column.SortDirection;
        if (sort == null)
            sort = ListSortDirection.Ascending;
        else if (sort == ListSortDirection.Ascending)
            sort = ListSortDirection.Descending;
        else
            sort = null;

        if (sort != null) {
            // first figure out correct group ordering
            var sortedGroups = dataGrid.ItemsSource.OfType<Item>()
                .GroupBy(c => c.GroupName)
                .Select(c => new {GroupName = c.Key, MinValue = c.Min(r => r.Value)})
                .OrderBy(c => c.MinValue)
                .Select(c => c.GroupName)
                .ToArray();
            // now set collection view custom sort to out comparer
            source.CustomSort = new ItemComparer(sortedGroups, sort == ListSortDirection.Ascending);
        }
        else {
            // otherwise remove custom sort and sort as usual
            source.CustomSort = null;
        }
        e.Column.SortDirection = sort;
        e.Handled = true;
    }
}

public class ItemComparer : IComparer {
    private readonly string[] _sortedGroups;
    private readonly bool _asc;

    public ItemComparer(string[] sortedGroups, bool asc) {
        _sortedGroups = sortedGroups;
        _asc = asc;
    }

    public int Compare(object ox, object oy) {
        var x = (Item) ox;
        var y = (Item) oy;

        if (x.GroupName == y.GroupName) {
            // if group names are the same - sort as usual, by Value
            return x.Value.CompareTo(y.Value) * (_asc ? 1 : -1);
        }
        // otherwise - sort by group name using the order we already figured out at previous step
        return (Array.IndexOf(_sortedGroups, x.GroupName) - Array.IndexOf(_sortedGroups, y.GroupName)) * (_asc ? 1 : -1);
    }
}