blocks|key|200170|text|在使用$array.Add()-method时，您尝试将元素添加到现有数组中。数组是一个固定大小的集合，因此您将收到一个错误，因为它不能被扩展。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|200171|$array+%2B=+$element使用与旧数组相同的元素%2B新项创建一个新数组，并且这个新的更大的数组将替换$array-variable中的旧数组|BOLD|200172|200173|可以使用%2B=运算符将元素添加到数组中。当你使用它时，Windows+PowerShell实际上会用原始数组的值和附加值创建一个新的数组。例如，要在$a变量中将值为200的元素添加到数组中，请键入：|blockquote|200174|200175|$a+%2B=+200|200176|200177|来源：about_Arrays|200178|%2B=是一个开销很大的操作，因此当您需要添加许多项时，您应该尝试在尽可能少的操作中添加它们，例如：|200179|$arr+=+1..3++++#Array
$arr+%2B=+(4..5)+#Combine+with+another+array+in+a+single+write-operation

$arr.Count
5|code-block|syntax|javascript|200180|如果这是不可能的，考虑使用更有效的集合，如List或ArrayList+(参见另一个答案)。|200181|entityMap|0|LINK|mutability|MUTABLE|url|http://technet.microsoft.com/en-us/library/hh847882.aspx^0|3|C|0|0|I|1I|6|10|1|0|0|0|0|0|0|3|C|0|0|0|2|0|0|L|4|Q|9|0^^$0|@$1|2|3|4|5|6|7|19|8|@$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1C|8|@$9|1D|A|1E|B|C]|$9|1F|A|1G|B|C]|$9|1H|A|1I|B|H]]|D|@]|E|$]]|$1|I|3|-4|5|6|7|1J|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|1K|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|1L|8|@]|D|@]|E|$]]|$1|N|3|O|5|6|7|1M|8|@]|D|@]|E|$]]|$1|P|3|-4|5|6|7|1N|8|@]|D|@]|E|$]]|$1|Q|3|R|5|6|7|1O|8|@]|D|@$9|1P|A|1Q|1|1R]]|E|$]]|$1|S|3|T|5|6|7|1S|8|@$9|1T|A|1U|B|C]]|D|@]|E|$]]|$1|U|3|V|5|W|7|1V|8|@]|D|@]|E|$X|Y]]|$1|Z|3|10|5|6|7|1W|8|@$9|1X|A|1Y|B|C]|$9|1Z|A|20|B|C]]|D|@]|E|$]]|$1|11|3|-4|5|6|7|21|8|@]|D|@]|E|$]]]|12|$13|$5|14|15|16|E|$17|18]]]]

When using the <code>$array.Add()</code>-method, you're trying to add the element into the existing array. An array is a collection of fixed size, so you will receive an error because it can't be extended.

<code>$array += $element</code> creates a new array with the same elements as old one + the new item, and this new larger array replaces the old one in the <code>$array</code>-variable 

<blockquote>
 You can use the += operator to add an element to an array. When you
 use
 it, Windows PowerShell actually creates a new array with the values of the
 original array and the added value. For example, to add an element with a 
 value of 200 to the array in the $a variable, type:

<pre><code> $a += 200
</code></pre>
</blockquote>

Source: <a href="http://technet.microsoft.com/en-us/library/hh847882.aspx" rel="noreferrer">about_Arrays</a>

<code>+=</code> is an expensive operation, so when you need to add many items you should try to add them in as few operations as possible, ex:

<pre><code>$arr = 1..3 #Array
$arr += (4..5) #Combine with another array in a single write-operation

$arr.Count
5
</code></pre>

If that's not possible, consider using a more efficient collection like <code>List</code> or <code>ArrayList</code> (see the other answer).

blocks|key|2829693|text|如果你想要一个动态大小的数组，那么你应该做一个列表。您不仅可以获得.Add()功能，而且正如@frode-f所解释的那样，动态数组的内存效率更高，而且也是一种更好的实践。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2829694|而且它使用起来非常简单。|2829695|尝试下面的代码，而不是数组声明：|2829696|$outItems+=+New-Object+System.Collections.Generic.List[System.Object]|code-block|syntax|javascript|2829697|添加项目很简单。|2829698|$outItems.Add(1)
$outItems.Add("hi")|2829699|如果你真的想要一个数组，当你完成时，也有一个函数。|2829700|$outItems.ToArray()|2829701|entityMap^0|X|6|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|11|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|12|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|13|8|@]|D|@]|E|$M|N]]|$1|O|3|P|5|6|7|14|8|@]|D|@]|E|$]]|$1|Q|3|R|5|L|7|15|8|@]|D|@]|E|$M|N]]|$1|S|3|T|5|6|7|16|8|@]|D|@]|E|$]]|$1|U|3|V|5|L|7|17|8|@]|D|@]|E|$M|N]]|$1|W|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|X|$]]

If you want a dynamically sized array, then you should make a list. Not only will you get the <code>.Add()</code> functionality, but as @frode-f explains, dynamic arrays are more memory efficient and a better practice anyway.

And it's so easy to use.

Instead of your array declaration, try this:

<pre><code>$outItems = New-Object System.Collections.Generic.List[System.Object]
</code></pre>

Adding items is simple.

<pre><code>$outItems.Add(1)
$outItems.Add("hi")
</code></pre>

And if you really want an array when you're done, there's a function for that too.

<pre><code>$outItems.ToArray()
</code></pre>

blocks|key|197383|text|要在不使用低效%2B=的情况下创建数组，最常见的习惯用法是从循环的输出中创建数组：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|197384|$array+=+foreach($i+in+1..10)+{+
++$i
}
$array|code-block|syntax|javascript|197385|[collections.arraylist]$array+=+1..10
$array.add(11)+>+$null|197386|entityMap^0|7|2|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|H|7|S|8|@]|D|@]|E|$I|J]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

The most common idiom for creating an array without using the inefficient <code>+=</code> is something like this, from the output of a loop:
<pre><code>$array = foreach($i in 1..10) { 
 $i
}
$array
</code></pre>
<pre><code>[collections.arraylist]$array = 1..10
$array.add(11) &gt; $null
</code></pre>

I've found some interesting behaviour in PowerShell Arrays, namely, if I declare an array as:

<pre><code>$array = @()
</code></pre>

And then try to add items to it using the <code>$array.Add("item")</code> method, I receive the following error:

<blockquote>
 Exception calling "Add" with "1" argument(s): "Collection was of a fixed size."
</blockquote>

However, if I append items using <code>$array += "item"</code>, the item is accepted without a problem and the "fixed size" restriction doesn't seem to apply.

Why is this?

Array.Add vs +=

Windows

我在PowerShell数组中发现了一些有趣的行为，即如果我将一个数组声明为：$array = @()然后尝试使用$array.Add("item")方法向其中添加项，我收到以下错误：使用"1“参数调用"Add”时发生异常：“集合大小固定。”但是，如果我使用$array += "item"附加项目，项目会被毫无问题地接...

问Array.Add vs +=
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