CODEWITHSUNDEEP
c#
Jyoti
Jyoti

Reputation: 121

add an item to the queue only if it does not exist in queue

I am processing zip files using queue. So whenever a new zip file arrives to the specified path, file_info will be added to queue using
fileQueue.Enqueue(IFile); Now I should add the File to queue only if it does not exist. I tried to implement IEqualityComparer<T> interface and the 

public bool Equals(T x, T y)
{
   object xValue = _propertyInfo.GetValue(x, null);
   object yValue = _propertyInfo.GetValue(y, null);
   return xValue.Equals(yValue);
}

and 

public int GetHashCode(T obj)
{
   object propertyValue = _propertyInfo.GetValue(obj, null);
   if (propertyValue == null)
      return 0;
   else
      return propertyValue.GetHashCode();
}

I have an interface to get the fileInfo 

public interface IFile
{        
   string FilePath { get; set; }
}

Another queue object

public Queue<IFile> fileQueue = new Queue<IFile>();

Can anyone please suggest how to check if the file already exists in the queue before adding it to the queue again. Thanks you very much in advance.

Upvotes: 2

Views: 2541

Answers (2)

Marty
Marty

Reputation: 3555

If You want a fast performing solution (and want to avoid iterating over the whole queue each time You add smth) You'll need to implement Your own queue.

smth like this

public class MyQueue
{
    private Queue<IFile> _queue;
    private HashSet<int> hashes;

    public void Add(IFile file)
    {
        var hash = GetHash(file);
        if (hashes.Add(hash))
        {
            _queue.Enqueue(file);
        }
    }
}

Basically have a "table of contents" - that is implemented as a hashset (that is used to hold a list of unique values)

NOTE: once You start using queues, and messages - the whole idea behind such architecture - is that messages should be idempotent. Which means - it doesn't matter it You add the same message to the queue multiple times.

Upvotes: 3

Magnus
Magnus

Reputation: 46947

if(!fileQueue.Any(x => x.FilePath == file.FilePath))
   fileQueue.Enqueue(file)

Upvotes: 1

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