blocks|key|576110|text|您可以尝试如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|576111|var+nulls+=+table.Where(x+=>+x.NullableDateTimeField+==+null);
var+notNulls+=+table.Where(x+=>+x.NullableDateTimeField+!=+null);

var+result+=+nulls.Concat(notNulls.OrderByDescending(x+=>+x.NullableDateTimeField));|code-block|syntax|javascript|576112|它“显然是正确的”，而不是“可能是超级高效的”，但它至少是一个起点。|576113|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

You could try something like this:

<pre><code>var nulls = table.Where(x =&gt; x.NullableDateTimeField == null);
var notNulls = table.Where(x =&gt; x.NullableDateTimeField != null);

var result = nulls.Concat(notNulls.OrderByDescending(x =&gt; x.NullableDateTimeField));
</code></pre>

It's more "obviously correct" than "likely to be super-efficient", but it's at least a starting point.

blocks|key|792451|text|您可以从排序表达式中返回DateTime.MaxValue而不是null，因此具有null日期的行将首先排序：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|792452|yourData.OrderByDescending(row+=>+row.dateTimeField+??+DateTime.MaxValue);|code-block|syntax|javascript|792453|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/system.datetime.maxvalue.aspx^0|W|4|15|4|C|H|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]]|E|$]]|$1|F|3|G|5|H|7|10|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

You can return <a href="http://msdn.microsoft.com/en-us/library/system.datetime.maxvalue.aspx">DateTime.MaxValue</a> instead of <code>null</code> from the ordering expression, so rows with <code>null</code> dates are sorted first:

<pre><code>yourData.OrderByDescending(row =&gt; row.dateTimeField ?? DateTime.MaxValue);
</code></pre>

blocks|key|792499|text|我发现最直接的方法是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|792500|data.OrderBy(Function(o)+o.myDate+IsNot+Nothing).ThenByDescending(Function(o)+o.myDate)|code-block|syntax|javascript|792501|在C#我认为..。|792502|data.OrderBy(o+=>+o.myDate+!=+null).ThenByDescending(o+=>+o.myDate)|792503|这也适用于LINQ+to+SQL。我不确定if(nullable,+value)是否会成功地转换成SQL。|offset|length|style|CODE|792504|entityMap^0|0|0|0|0|L|J|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@$M|X|N|Y|O|P]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

I find the most straightforward approach to be:

<pre><code>data.OrderBy(Function(o) o.myDate IsNot Nothing).ThenByDescending(Function(o) o.myDate)
</code></pre>

in C# I think...

<pre><code>data.OrderBy(o =&gt; o.myDate != null).ThenByDescending(o =&gt; o.myDate)
</code></pre>

This will also work with LINQ to SQL. I'm not sure if <code>if(nullable, value)</code> will successfully translate to SQL.

blocks|key|576250|text|看一看David+Oesterreich's+blog:|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|576251|var+queryResult+=
orderedProducts+from+enumerableProducts
order+by+orderedProducts.ProductName,
orderedProducts.Price+!=+null+?+1+:+0+descending,
orderedProducts.Price
select+orderedProducts;|code-block|syntax|javascript|576252|entityMap|0|LINK|mutability|MUTABLE|url|https://web.archive.org/web/20130121060553/http://www.davidoesterreich.com/blog/linq-sort-by-nulls-last/^0|3|P|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Take a look at <a href="https://web.archive.org/web/20130121060553/http://www.davidoesterreich.com/blog/linq-sort-by-nulls-last/" rel="nofollow">David Oesterreich's blog:</a>

<pre><code>var queryResult =
orderedProducts from enumerableProducts
order by orderedProducts.ProductName,
orderedProducts.Price != null ? 1 : 0 descending,
orderedProducts.Price
select orderedProducts;
</code></pre>

blocks|key|792607|text|与上面接受的版本类似，但具有用于c#+v6的语法|type|unstyled|depth|inlineStyleRanges|entityRanges|data|792608|tickets.OrderByDescending(x+=>+x?.Erstellt+??+DateTime.Now)|code-block|syntax|javascript|792609|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

like the accepted version above but with syntax for c# v6

<pre><code>tickets.OrderByDescending(x =&gt; x?.Erstellt ?? DateTime.Now)
</code></pre>

I have a field in my database that holds a DateTime?. I would like to sort the results so that the NULLs show up at the top, then descending by DateTime, e.g.,

<pre><code>null
null
2012-04-01
2012-01-01
2011-09-04
</code></pre>

The reason is that I am looking at expiration dates, though some entries do not expire.

Linq OrderByDescending, null first

数据库

我的数据库中有一个包含DateTime?的字段。我希望对结果进行排序，使空值显示在顶部，然后按DateTime降序，例如，nullnull2012-04-012012-01-012011-09-04原因是我正在查看过期日期，尽管有些条目不会过期。

问Linq OrderByDescending，第一个为空
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