关于 c#:Group by range using linq

c#group-bylinqrange

Group by range using linq

本问题已经有最佳答案，请猛点这里访问。

我们如何使用分组范围等于或大于？

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var data = new[] {
new { Id = 0, Price = 2 },
new { Id = 1, Price = 10 },
new { Id = 2, Price = 30 },
new { Id = 3, Price = 50 },
new { Id = 4, Price = 120 },
new { Id = 5, Price = 200 },
new { Id = 6, Price = 1024 },
};

var ranges = new[] { 10, 50, 100, 500 };
var grouped = data.GroupBy( x => ranges.FirstOrDefault( r => r > x.Price ) );

grouped ouput is
price 10-50 -> 3
price 50-100 -> 1
price 100-500 -> 2

需要的输出按等于或大于使用的范围分组

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price >= 10 -> 6
price >= 50 -> 4
price >= 100 -> 3
price >= 500 -> 1

相关讨论

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var grouped = ranges.Select(r => new {
Price = r,
Count = data.Where(x => x.Price >= r).Count() });

还有另一个选择(如果你有大量数据，那么分组比枚举每个价格组的所有数据要好)：

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var priceGroups = data.GroupBy(x => ranges.FirstOrDefault(r => r > x.Price))
.Select(g => new { Price = g.Key, Count = g.Count() })
.ToList();

var grouped = ranges.Select(r => new
{
Price = r,
Count = priceGroups.Where(g => g.Price > r || g.Price == 0).Sum(g => g.Count)
});

相关讨论

分组对源进行分区，每个项目分配到一个组。

你所拥有的是一个好的开始：

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var data = new[] {
new { Id = 0, Price = 2 },
new { Id = 1, Price = 10 },
new { Id = 2, Price = 30 },
new { Id = 3, Price = 50 },
new { Id = 4, Price = 120 },
new { Id = 5, Price = 200 },
new { Id = 6, Price = 1024 },
};

var ranges = new[] { 10, 50, 100, 500 };
var grouped = data.GroupBy( x => ranges.FirstOrDefault( r => r <= x.Price ) );

跟进：

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int soFar = 0;
Dictionary<int, int> counts = grouped.ToDictionary(g => g.Key, g => g.Count());
foreach(int key in counts.Keys.OrderByDescending(i => i))
{
soFar += counts[key];
counts[key] = soFar;
}

或者如果你想在一个 linq 语句中做到这一点：

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int soFar = 0;
var grouped = data
.GroupBy( x => ranges.FirstOrDefault( r => r <= x.Price ) )
.OrderByDescending(g => g.Key)
.Select(g =>
{
soFar += g.Count();
return new Tuple<int, int>(g.Key, soFar)
});