使用 LINQ 透视数据 [英] Pivot data using LINQ

问题描述

我有一个包含 Enum (TypeCode) 和 User 对象的项目集合，我需要将其展平以显示在网格中.这很难解释，所以让我举一个简单的例子.

I have a collection of items that contain an Enum (TypeCode) and a User object, and I need to flatten it out to show in a grid. It's hard to explain, so let me show a quick example.

Collection 有这样的项目:

Collection has items like so:

TypeCode | User 
---------------
1        | Don Smith  
1        | Mike Jones  
1        | James Ray  
2        | Tom Rizzo  
2        | Alex Homes  
3        | Andy Bates  

我需要输出:

1          | 2          | 3  
Don Smith  | Tom Rizzo  | Andy Bates  
Mike Jones | Alex Homes |  
James Ray  |            |  

我已经尝试使用 foreach 来做到这一点，但我不能这样做，因为我会在 foreach 的集合中插入新项目，从而导致错误.

I've tried doing this using foreach, but I can't do it that way because I'd be inserting new items to the collection in the foreach, causing an error.

这可以在 Linq 中以更简洁的方式完成吗?

Can this be done in Linq in a cleaner fashion?

推荐答案

我不是说它是一种伟大的 枢轴方式 - 但它是一个枢轴......

I'm not saying it is a great way to pivot - but it is a pivot...

    // sample data
    var data = new[] {
        new { Foo = 1, Bar = "Don Smith"},
        new { Foo = 1, Bar = "Mike Jones"},
        new { Foo = 1, Bar = "James Ray"},
        new { Foo = 2, Bar = "Tom Rizzo"},
        new { Foo = 2, Bar = "Alex Homes"},
        new { Foo = 3, Bar = "Andy Bates"},
    };
    // group into columns, and select the rows per column
    var grps = from d in data
              group d by d.Foo
              into grp
              select new {
                  Foo = grp.Key,
                  Bars = grp.Select(d2 => d2.Bar).ToArray()
              };

    // find the total number of (data) rows
    int rows = grps.Max(grp => grp.Bars.Length);

    // output columns
    foreach (var grp in grps) {
        Console.Write(grp.Foo + "	");
    }
    Console.WriteLine();
    // output data
    for (int i = 0; i < rows; i++) {
        foreach (var grp in grps) {
            Console.Write((i < grp.Bars.Length ? grp.Bars[i] : null) + "	");
        }
        Console.WriteLine();
    }

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