How could I determine if an array contains a value at a particular index?

I have an array with values at meaningful indices. How can I tell if a particular there is a value at a particular element?

Array.Exists() is the closest I've found, but it looks overcomplicated for what I want, so I'm curious to know if it's really the best way.

UPDATE

OK, so I have开发者_运维技巧 an array of objects:

ImageGroup[] Images;

And the index of the elements corresponds to a feature of that item. In this case, the index refers to a value within the filename of the original image. When I come across a filename, I want to check if an element exists at the corresponding index and create one if not.

So I want to know if Images[someInt] exists.

Updated

With the last update this looks more like a dictionary (unless you're going in numerical order and not where "1,2,5" may have been populated, but 3,4 are absent and need to be created). If this is something where index could potentially skip, I would recommend a dictionary:

Dictionary<Int32,Image> images = new Dictionary<Int32, Image>();
// populated previously

Int32 needle = GetIndexOfImage(newImage);
if (!images.ContainsKey(needle))
  images.Add(needle, newImage);

Then, once you're done populating, you can then re-reference the item by index in the following fashion:

images[specificIndex]

Once more, you can retrieve all the elements stored using the following as well:

images.Values

Some resources:

• Dictionary
• Dictionary.ContainsKey

First response:

 if (a[index] == interesting) ....

After the Edit(s):

int index = GetIndexFromFilename(filename);
// if (Images[index] != null && Images[index] == interesting) ....
if (Images[index] == null)
    Images[index] = CreateImage(filename);

But you should probably just use a Dictionary<string, Image> and use filename as the Key.

It sounds like what you're looking for is the functionality of a dictionary. It would be extremely helpful if you posted how you're populating your array, and how you want to be able to index it. From what I can gather, this is how I would implement...

Dictionary<SomeEnum, ImageGroup> images = new Dictionary<SomeEnum, ImageGroup>();
foreach(SomeEnum enumValue in Enum.GetValues(typeof(SomeEnum)))
{
   ImageGroup group = BuildImageGroup();
   images.Add(enumValue, group);
}

then you can do:

...
if(images.ContainsKey(SomeEnum.SomeValue))
   return images[SomeEnum.SomeValue];
else
   return DoSomethingFancy();

If you have multiple image groups for a single enum value (collisions), then you can use a collection of ImageGroups in the dictionary, like this:

Dictionary<SomeEnum, ImageGroup[]>