blocks|key|1573303|text|测试长度|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1573304|int+index+=+25;
if(index+<+array.Length)
{
++++//it+exists
}|code-block|syntax|javascript|1573305|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|$]]

Test the length

<pre><code>int index = 25;
if(index &lt; array.Length)
{
 //it exists
}
</code></pre>

blocks|key|1573711|text|你也可以使用LINQ来实现：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1573712|var+exists+=+array.ElementAtOrDefault(index)+!=+null;|code-block|syntax|javascript|1573713|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|$]]

You can use LINQ to achieve that too:

<pre><code>var exists = array.ElementAtOrDefault(index) != null;
</code></pre>

blocks|key|1573377|text|你所说的“是一个有效元素”到底是什么意思？你可以这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1573378|if+(array.Length+>=+26)|code-block|syntax|javascript|1573379|它将告诉您25是否是数组中的有效索引(假设下限为0)。|1573380|如果您需要知道它是否是非空的，只需使用：|1573381|if+(array[25]+!=+null)|1573382|(或两者的组合)。|1573383|如果这些都不起作用，请为您的问题提供更准确的“有效”含义。|1573384|entityMap^0|0|0|0|0|0|0|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]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|W|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

What exactly do you mean by "is a valid element"? You could just do:

<pre><code>if (array.Length &gt;= 26)
</code></pre>

which would tell you whether 25 is a valid index into the array or not (assuming a 0 lower bound).

If you need to know whether it's non-null or not, just use:

<pre><code>if (array[25] != null)
</code></pre>

(or a combination of the two).

If these don't help, please give a more precise meaning of "valid" for your problem.

blocks|key|1573325|text|假设您还想检查该项是否不为空|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1573326|if+(array.Length+>+25+&&+array[25]+!=+null)
{
++++//it+exists
}|code-block|syntax|javascript|1573327|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 you also want to check if the item is not null 

<pre><code>if (array.Length &gt; 25 &amp;&amp; array[25] != null)
{
 //it exists
}
</code></pre>

blocks|key|1573692|text|//+I'd+modify+this+slightly+to+be+more+resilient+to+a+bad+parameter
//+it+will+handle+your+case+and+better+handle+other+cases+given+to+it:

int+index+=+25;

if+(index+>=+0+&&+index+<+array.Length)
{
++++//+Array+element+found
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1573693|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>// I'd modify this slightly to be more resilient to a bad parameter
// it will handle your case and better handle other cases given to it:

int index = 25;

if (index &gt;= 0 &amp;&amp; index &lt; array.Length)
{
 // Array element found
}
</code></pre>

blocks|key|1573425|text|您可以使用数组的长度，并查看您的任意数字是否适合该范围。例如，如果您有一个大小为10的数组，那么array25是无效的，因为25不小于10。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1573426|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

You can use the length of the array, and see if your arbitrary number fits in that range. For example, if you have an array of size 10, then array[25] isn't valid because 25 is not less than 10.

blocks|key|1573485|text|你可以使用列表，这样你就可以检查它的存在。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1573486|List<int>+l+=+new+List<int>();
l.Add(45);
...
...

if+(l.Count+==+25)+{
++doStuff();
}
int+num+=+45;
if+(l.Contains(num))+{
++doMoreStuff();
}|code-block|syntax|javascript|1573487|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|$]]

You can rather use a List, so you can check the existence.

<pre><code>List&lt;int&gt; l = new List&lt;int&gt;();
l.Add(45);
...
...

if (l.Count == 25) {
 doStuff();
}
int num = 45;
if (l.Contains(num)) {
 doMoreStuff();
}
</code></pre>

blocks|key|1573513|text|array.length将告诉您一个数组中有多少个元素|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1573514|entityMap^0|0|C|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

<code>array.length</code> will tell you how many elements are in an array

blocks|key|1573780|text|这里的答案很简单，但只适用于一维数组。对于多维数组，检查null是判断元素是否存在的一种直接方法。这里的示例代码检查是否为空。注意try/catch块可能是杀伤力过大，但它使块变得防弹。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1573781|public+ItemContext+GetThisElement(int+row,
++++int+col)
{
++++ItemContext+ctx+=+null;
++++if+(rgItemCtx[row,+col]+!=+null)
++++{
++++++++try
++++++++{
++++++++++ctx+=+rgItemCtx[row,+col];
++++++++}
++++++++catch+(SystemException+sex)
++++++++{
++++++++++ctx+=+null;
++++++++++//+perhaps+do+something+with+sex+properties
++++++++}
++++}

++++return+(ctx);
}|code-block|syntax|javascript|1573782|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|$]]

The answers here are straightforward but only apply to a 1 dimensional array.
For multi-dimensional arrays, checking for null is a straightforward way to tell if the element exists. Example code here checks for null. Note the try/catch block is [probably] overkill but it makes the block bomb-proof.
<pre><code>public ItemContext GetThisElement(int row,
 int col)
{
 ItemContext ctx = null;
 if (rgItemCtx[row, col] != null)
 {
 try
 {
 ctx = rgItemCtx[row, col];
 }
 catch (SystemException sex)
 {
 ctx = null;
 // perhaps do something with sex properties
 }
 }

 return (ctx);
}
</code></pre>

blocks|key|1573571|text|您可以检查索引是否小于数组的长度。这不会检查空值或其他奇怪的情况，在这些情况下，可以为索引赋值，但没有显式地给索引赋值。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1573572|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

You could check if the index is less than the length of the array. This doesn't check for nulls or other odd cases where the index can be assigned a value but hasn't been given one explicitly.

blocks|key|1358335|text|可以检查数组的长度，看看25项在数组中是否有效，然后可以使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1358336|if+(array.Length+>+25)
{+
+++if+(array[25]+!=+null)
+++{
+++++++//good
+++}
}|code-block|syntax|javascript|1358337|以查看数组项本身是否已设置。|1358338|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 can check the length of the array to see if item 25 is valid in the sense of being in the array, then you could use 

<pre><code>if (array.Length &gt; 25)
{ 
 if (array[25] != null)
 {
 //good
 }
}
</code></pre>

to see if the array item itself has been set.

blocks|key|1358419|text|听起来很像是使用一个数组来存储不同的字段。这绝对是代码的味道。我尽量避免使用数组，因为它们通常不适合(或不需要)在高级代码中使用。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1358420|在短期内，切换到简单字典可能是一个可行的选择。就像使用一个大的属性包类一样。有很多选择。你现在的问题只是糟糕设计的症状，你应该着眼于修复潜在的问题，而不是仅仅修补糟糕的设计，所以现在它基本上是有效的。|1358421|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

It sounds very much like you're using an array to store different fields. This is definitely a code smell. I'd avoid using arrays as much as possible as they're generally not suitable (or needed) in high-level code.

Switching to a simple Dictionary may be a workable option in the short term. As would using a big property bag class. There are lots of options. The problem you have now is just a symptom of bad design, you should look at fixing the underlying problem rather than just patching the bad design so it kinda, sorta mostly works, for now.

I've inherited some code at work that has a really bad smell. I'm hoping to find the most painless solution possible.

Is there a way to check if some arbitrary number is a valid element in an array?

Example - I need to check if array[25] exists.

Preferably I would prefer to do this without doing a foreach() through the array to found the rows.

Is there any way to do this, or am I stuck with foreach loop?

Does Index of Array Exist

我在工作中继承了一些很难闻的代码。我希望能找到最无痛的解决方案。有没有办法检查某个任意数是否为数组中的有效元素？示例-我需要检查array25是否存在。我更喜欢这样做，而不是通过对数组执行foreach()来查找行。有没有办法做到这一点，或者我被foreach循环卡住了？

问数组的索引是否存在
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