blocks|key|3973225|text|一种选择是添加它们并删除重复的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3973226|var+list+=+new+List<Car>();
list.AddRange(GetGreenCars());
list.AddRange(GetBigCars());
list.AddRange(GetSmallCars());
list+=+list.Distinct().ToList();|code-block|syntax|javascript|3973227|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|$]]

One choice is to add them and remove the repeated ones:

<pre><code>var list = new List&lt;Car&gt;();
list.AddRange(GetGreenCars());
list.AddRange(GetBigCars());
list.AddRange(GetSmallCars());
list = list.Distinct().ToList();
</code></pre>

blocks|key|1216025|text|在这里，List<T>似乎不是合适的集合。您可能需要像HashSet这样的ISet<T>实现(如果需要排序，则可以使用SortedSet+)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1216026|要实现这一点，您需要编写一个根据Name属性定义汽车之间相等的IEqualityComparer<T>实现。如果这是汽车相等的“规范”定义，您也可以考虑直接将此定义构建到Car类型本身中(object.Equals、object.GetHashCode，理想情况下也可以实现IEquatable<T>+)。|1216027|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/bb359438.aspx|1|http://msdn.microsoft.com/en-us/library/dd412070.aspx^0|4|7|R|7|11|7|1N|9|R|7|0|1N|9|1|0|G|4|V|K|2D|3|2M|D|30|I|3T|D|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@$9|10|A|11|1|12]|$9|13|A|14|1|15]]|E|$]]|$1|F|3|G|5|6|7|16|8|@$9|17|A|18|B|C]|$9|19|A|1A|B|C]|$9|1B|A|1C|B|C]|$9|1D|A|1E|B|C]|$9|1F|A|1G|B|C]|$9|1H|A|1I|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|1J|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]|P|$5|K|L|M|E|$N|Q]]]]

A <code>List&lt;T&gt;</code> doesn't seem to be the appropriate collection here. You probably want an <code>ISet&lt;T&gt;</code> implementation such as <a href="http://msdn.microsoft.com/en-us/library/bb359438.aspx"><code>HashSet&lt;T&gt;</code></a> (or <a href="http://msdn.microsoft.com/en-us/library/dd412070.aspx"><code>SortedSet&lt;T&gt;</code></a> if you need ordering).

To allow this, you will need to write an <code>IEqualityComparer&lt;T&gt;</code> implementation that defines equality between cars according to the <code>Name</code> property. If this is the 'canonical' definition of car-equality, you can also consider directly building this definition into the <code>Car</code> type itself (<code>object.Equals</code>, <code>object.GetHashCode</code> and ideally implement <code>IEquatable&lt;T&gt;</code> too).

blocks|key|199099|text|另一种选择是做一些类似的事情：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|199100|public+static+void+AddUnique<T>(+this+IList<T>+self,+IEnumerable<T>+items+)
{
++++foreach(var+item+in+items)
++++++++if(!self.Contains(item))
++++++++++++self.Add(item);
}


var+list+=+new+List<Car>();
list.AddUnique(GetGreenCars());
list.AddUnique(GetBigCars());
list.AddUnique(GetSmallCars());|code-block|syntax|javascript|199101|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|$]]

Another option is to do something like:

<pre><code>public static void AddUnique&lt;T&gt;( this IList&lt;T&gt; self, IEnumerable&lt;T&gt; items )
{
 foreach(var item in items)
 if(!self.Contains(item))
 self.Add(item);
}


var list = new List&lt;Car&gt;();
list.AddUnique(GetGreenCars());
list.AddUnique(GetBigCars());
list.AddUnique(GetSmallCars());
</code></pre>

blocks|key|1218181|text|另一种选择是使用Linq：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1218182|public+static+void+AddUnique<T>(this+IList<T>+self,+IEnumerable<T>+items)
{
++self.AddRange(
++++items.Where(x+=>+self.FirstOrDefault(y+=>+y.Name+==+x.Name)+==
++++null).ToList());
}

var+list+=+new+List<Car>();
list.AddUnique(GetGreenCars());
list.AddUnique(GetBigCars());
list.AddUnique(GetSmallCars());|code-block|syntax|javascript|1218183|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|$]]

Yet another option using Linq:

<pre><code>public static void AddUnique&lt;T&gt;(this IList&lt;T&gt; self, IEnumerable&lt;T&gt; items)
{
 self.AddRange(
 items.Where(x =&gt; self.FirstOrDefault(y =&gt; y.Name == x.Name) ==
 null).ToList());
}

var list = new List&lt;Car&gt;();
list.AddUnique(GetGreenCars());
list.AddUnique(GetBigCars());
list.AddUnique(GetSmallCars());
</code></pre>

blocks|key|3973345|text|假设您覆盖了Car的.Equals()方法来确定一个car对象与另一个car对象相同，那么下面的代码应该不需要编写扩展方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3973346|++++var+list+=+new+List<Car>();
++++list.AddRange(GetGreenCars()?.Except(list)+??+new+List<Car>());
++++list.AddRange(GetBigCars()?.Except(list)+??+new+List<Car>());
++++list.AddRange(GetSmallCars()?.Except(list)+??+new+List<Car>());|code-block|syntax|javascript|3973347|entityMap^0|6|3|A|9|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

Given you override the <code>.Equals()</code> method for <code>Car</code> to determine one car object is the same as another car object, then the following should work w/o writing an extension method.

<pre class="lang-cs prettyprint-override"><code> var list = new List&lt;Car&gt;();
 list.AddRange(GetGreenCars()?.Except(list) ?? new List&lt;Car&gt;());
 list.AddRange(GetBigCars()?.Except(list) ?? new List&lt;Car&gt;());
 list.AddRange(GetSmallCars()?.Except(list) ?? new List&lt;Car&gt;());
</code></pre>

blocks|key|1218208|text|我创建了一个扩展方法，该方法只向从IEnumerable<T>实现ICollection<T>+(包括List<T>)的任何内容添加唯一值。与使用List<T>.Contains()的实现不同，此方法允许您指定一个λ表达式来确定两个项是否相同。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1218209|///+<summary>
///+Adds+only+items+that+do+not+exist+in+source.++May+be+very+slow+for+large+collections+and+some+types+of+source.
///+</summary>
///+<typeparam+name="T">Type+in+the+collection.</typeparam>
///+<param+name="source">Source+collection</param>
///+<param+name="predicate">Predicate+to+determine+whether+a+new+item+is+already+in+source.</param>
///+<param+name="items">New+items.</param>
public+static+void+AddUniqueBy<T>(this+ICollection<T>+source,+Func<T,+T,+bool>+predicate,+IEnumerable<T>+items)
{
++++foreach+(T+item+in+items)
++++{
++++++++bool+existsInSource+=+source.Where(s+=>+predicate(s,+item)).Any();
++++++++if+(!existsInSource)+source.Add(item);
++++}
}|code-block|syntax|javascript|1218210|用法：|1218211|source.AddUniqueBy<Foo>((s,+i)+=>+s.Id+==+i.Id,+items);|1218212|entityMap^0|H|E|X|E|1F|7|21|I|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|P|$]]

I created an extension method that adds only unique values to anything implementing <code>ICollection&lt;T&gt;</code> (including a <code>List&lt;T&gt;</code>) from an <code>IEnumerable&lt;T&gt;</code>. Unlike implementations that use <code>List&lt;T&gt;.Contains()</code>, this method allows you to specify a lambda expression that determines if two items are the same. 

<pre><code>/// &lt;summary&gt;
/// Adds only items that do not exist in source. May be very slow for large collections and some types of source.
/// &lt;/summary&gt;
/// &lt;typeparam name="T"&gt;Type in the collection.&lt;/typeparam&gt;
/// &lt;param name="source"&gt;Source collection&lt;/param&gt;
/// &lt;param name="predicate"&gt;Predicate to determine whether a new item is already in source.&lt;/param&gt;
/// &lt;param name="items"&gt;New items.&lt;/param&gt;
public static void AddUniqueBy&lt;T&gt;(this ICollection&lt;T&gt; source, Func&lt;T, T, bool&gt; predicate, IEnumerable&lt;T&gt; items)
{
 foreach (T item in items)
 {
 bool existsInSource = source.Where(s =&gt; predicate(s, item)).Any();
 if (!existsInSource) source.Add(item);
 }
}
</code></pre>

Usage:

<pre><code>source.AddUniqueBy&lt;Foo&gt;((s, i) =&gt; s.Id == i.Id, items);
</code></pre>

blocks|key|5588339|text|如果您想要比较一个属性(在本例中为id)，这应该是可行的|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5588340|var+list+=+new+List<string>();
list.AddRange(GetGreenCars().Where(greencar+=>+!list.Contains(greencar,+car+=>+car.id+==+greencar.id)));
list.AddRange(GetBigCars().Where(bigcar+=>+!list.Contains(bigcar,+car+=>+car.id+==+bigcar.id)));
list.AddRange(GetSmallCars().Where(smallcar+=>+!list.Contains(smallcar,+car+=>+car.id+==+smallcar.id)));|code-block|syntax|javascript|5588341|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|$]]

and if you want to compare one property (id in this case), this should work

<pre><code>var list = new List&lt;string&gt;();
list.AddRange(GetGreenCars().Where(greencar =&gt; !list.Contains(greencar, car =&gt; car.id == greencar.id)));
list.AddRange(GetBigCars().Where(bigcar =&gt; !list.Contains(bigcar, car =&gt; car.id == bigcar.id)));
list.AddRange(GetSmallCars().Where(smallcar =&gt; !list.Contains(smallcar, car =&gt; car.id == smallcar.id)));
</code></pre>

blocks|key|1218234|text|Linq+-less选项！一个不同的选项，以防程序员不能或不想使用Linq。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1218235|var+list+=+new+List<Car>();
list.AddRange(GetGreenCars().FindAll((x)+=>+!list.Contains(x)));
list.AddRange(GetBigCars().FindAll((x)+=>+!list.Contains(x)));
list.AddRange(GetSmallCars().FindAll((x)+=>+!list.Contains(x)));|code-block|syntax|javascript|1218236|如果初始列表是空的，如上面的示例所示，您实际上可以避免使用FindAll(...)在第一个AddRange()上。|1218237|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|$]]

Linq-less option!
A different option in case the programmer cannot, or don't wanna use Linq.
<pre><code>var list = new List&lt;Car&gt;();
list.AddRange(GetGreenCars().FindAll((x) =&gt; !list.Contains(x)));
list.AddRange(GetBigCars().FindAll((x) =&gt; !list.Contains(x)));
list.AddRange(GetSmallCars().FindAll((x) =&gt; !list.Contains(x)));
</code></pre>
If the initial list is empty as in the example above, you can actually avoid using FindAll(...) on the first AddRange().

blocks|key|5588381|text|假设Get*+Car+()返回汽车列表，另一种选择可能是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5588382|var+list+=+new+List<Car>();
GetGreenCars().ForEach(c+=>+{+if+(!list.Contains(c))+list.Add(c);+});
GetBigCars().ForEach(c+=>+{+if+(!list.Contains(c))+list.Add(c);+});
GetSmallCars().ForEach(c+=>+{+if+(!list.Contains(c))+list.Add(c);+});|code-block|syntax|javascript|5588383|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|$]]

Assuming your Get*Cars() return Lists of Car, another option could be:

<pre><code>var list = new List&lt;Car&gt;();
GetGreenCars().ForEach(c =&gt; { if (!list.Contains(c)) list.Add(c); });
GetBigCars().ForEach(c =&gt; { if (!list.Contains(c)) list.Add(c); });
GetSmallCars().ForEach(c =&gt; { if (!list.Contains(c)) list.Add(c); });
</code></pre>

I have a list in C#:

<pre><code> var list = new List&lt;Car&gt;();
 list.AddRange(GetGreenCars());
 list.AddRange(GetBigCars());
 list.AddRange(GetSmallCars());
</code></pre>

the issue is that some of the same cars get returned in different functions and I don't want them in the list more than once. Each car has a unique Name attribute. Is there anyway I can have something like this above but will only add items if they are unique ?

Is there an AddUnique method similar to Addrange() for alist in C#

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我在C#中有一个列表： var list = new List<Car>(); list.AddRange(GetGreenCars()); list.AddRange(GetBigCars()); list.AddRange(GetSmallCars());问题是，一些...

问对于C#中的列表，是否有类似于Addrange()的AddUnique方法
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问对于C#中的列表，是否有类似于Addrange()的AddUnique方法EN