linq group by并选择不在group by中的多个列 [英] linq group by and select multiple columns not in group by

问题描述

我正在尝试使用linq-c#选择不在组中的多个列.

I'm trying to select multiple columns not in a group by using linq - c#.

使用linq，我尝试按ISNULL(fieldOne，'')，ISNULL(fieldTo，'')进行分组，然后为每个组选择field_One，field_Two，field_Three.因此，对于group by将返回的每一行，我想看到很多行.

Using linq, I'm trying to group by ISNULL(fieldOne,''),ISNULL(fieldTo,'') and then select field_One, field_Two, field_Three for each group. So for each row that the group by would return, I want to see numerous rows.

到目前为止，我有以下内容，但似乎无法选择所有需要的列.

So far I have the following, but can't seem to select all the needed columns.

var xy = tableQueryable.Where(
            !string.IsNullOrEmpty(cust.field_One)
            || ! string.IsNullOrEmpty(ust.field_Two)
            ).GroupBy(cust=> new { field_One= cust.field_One ?? string.Empty, field_Tow = cust.field_Two  ?? string.Empty}).Where(g=>g.Count()>1).AsQueryable();

有人可以帮忙吗?

推荐答案

您几乎在那里-所缺少的只是该组中的Select:

You are pretty much there - all you are missing is a Select from the group:

var xy = tableQueryable
    .Where(!string.IsNullOrEmpty(cust.first_name) || ! string.IsNullOrEmpty(ust.lastName))
    .GroupBy(cust=> new { first_name = cust.first_name ?? string.Empty, last_name = cust.last_name ?? string.Empty})
    .Where(g=>g.Count()>1)
    .ToList() // Try to work around the cross-apply issue
    .SelectMany(g => g.Select(cust => new {
        Id = cust.Id
    ,   cust.FirstName
    ,   cust.LastName
    ,   cust.RepId
    }));

每个组中的

Select进行所需字段的投影，而SelectMany将所有结果转储到平面列表中.

Select from each group does the projection of the fields that you want, while SelectMany dumps all the results into a flat list.

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