Does Index of Array Exist

Question

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

User · Answer

You can use LINQ to achieve that too   var exists   array ElementAtOrDefault index     null

User · Answer

Assuming you also want to check if the item is not null     if  array Length  gt  25  amp  amp  array 25     null          it exists

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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

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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

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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

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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   if  array Length  gt  25        if  array 25     null                good          to see if the array item itself has been set

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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  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

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array length will tell you how many elements are in an array

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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

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

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What exactly do you mean by  is a valid element   You could just do   if  array Length  gt   26    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   if  array 25     null     or a combination of the two    If these don t help  please give a more precise meaning of  valid  for your problem

User · Answer

Test the length  int index   25  if index  lt  array Length          it exists

[c#] Does Index of Array Exist

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