如何使用 LINQ 执行 SELECT UNIQUE？

发布于 2024-09-15 05:05:06 字数 772 浏览 16 评论 0原文

我有一个这样的列表：

Red
Red
Brown
Yellow
Green
Green
Brown
Red
Orange

我正在尝试使用 LINQ 执行 SELECT UNIQUE，即我希望

Red
Brown
Yellow
Green
Orange

var uniqueColors = from dbo in database.MainTable
                   where dbo.Property == true
                   select dbo.Color.Name;

将其更改为

var uniqueColors = from dbo in database.MainTable
                   where dbo.Property == true
                   select dbo.Color.Name.Distinct();

但没有成功。第一个 select 获取所有颜色，那么如何修改它以仅获取唯一值？

如果有更好的方法来构造此查询，我们非常乐意采用该方法。

我该如何编辑它，以便可以拥有 .OrderBy( "column name" ) 即按颜色名称的字母顺序排列，即 name 属性？

我不断收到一条消息：

无法从用法推断类型参数。尝试显式指定类型参数。

原文

I have a list like this:

Red
Red
Brown
Yellow
Green
Green
Brown
Red
Orange

I am trying to do a SELECT UNIQUE with LINQ, i.e. I want

Red
Brown
Yellow
Green
Orange

var uniqueColors = from dbo in database.MainTable
                   where dbo.Property == true
                   select dbo.Color.Name;

I then changed this to

var uniqueColors = from dbo in database.MainTable
                   where dbo.Property == true
                   select dbo.Color.Name.Distinct();

with no success. The first select gets ALL the colors, so how do I modify it to only get the unique values?

If there is a better way of structuring this query, more than happy to go that route.

How do I go about editing it so I can have .OrderBy( "column name" ) i.e. alphabetically by color name, so name property?

I keep getting a message:

The type arguments cannot be inferred from the usage. Try specifying the type arguments explicitly.

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帅冕 2024-09-22 05:05:07

Distinct() 会打乱排序，因此您必须在此之后进行排序。

var uniqueColors = 
               (from dbo in database.MainTable 
                 where dbo.Property == true 
                 select dbo.Color.Name).Distinct().OrderBy(name=>name);

The Distinct() is going to mess up the ordering, so you'll have to the sorting after that.

var uniqueColors = 
               (from dbo in database.MainTable 
                 where dbo.Property == true 
                 select dbo.Color.Name).Distinct().OrderBy(name=>name);

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时光倒影 2024-09-22 05:05:07

var uniqueColors = (from dbo in database.MainTable 
                    where dbo.Property == true
                    select dbo.Color.Name).Distinct();

var uniqueColors = (from dbo in database.MainTable 
                    where dbo.Property == true
                    select dbo.Color.Name).Distinct();

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何时共饮酒 2024-09-22 05:05:07

使用查询理解语法，您可以实现 orderby，如下所示：

var uniqueColors = (from dbo in database.MainTable
                    where dbo.Property
                    orderby dbo.Color.Name ascending
                    select dbo.Color.Name).Distinct();

Using query comprehension syntax you could achieve the orderby as follows:

var uniqueColors = (from dbo in database.MainTable
                    where dbo.Property
                    orderby dbo.Color.Name ascending
                    select dbo.Color.Name).Distinct();

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