How to add List object to Dictionary

Question

How to add List<Dictionary<string, byte[]> object to Dictionary<string, byte[]>

public static async void PostUploadtoCloud( List<Dictionary<string, byte[]>> _commonFileCollection)
{
    Dictionary<string, Byte[]> _dickeyValuePairs = new Dictionary<string, byte[]>();

    foreach (var item in _commonFileCollection)
    {
        _dickeyValuePairs.add(item.key,item.value); // i want this but I am getting
        //_dickeyValuePairs.Add(item.Keys, item.Values); so I am not able to add it dictionary local variable _dickeyValuePairs 
    }
}

In foreach loop I am getting item.KEYS and item.VALUES so how I can add to it _dickeyValuePairs

Surely you need a nested `foreach` - `item` in your current loop is a `Dictionary`. — ProgrammingLlama, Aug 23 '18 at 06:47
Each `item` from `_commonFileCollection` would appear to be a *dictionary* itself. If you're wanting to work with the items *within* that dictionary, looks like you need an inner loop. — Damien_The_Unbeliever, Aug 23 '18 at 06:48

eocron · Accepted Answer · 2018-08-23T07:07:32.570

If you want to merge them, then something like this:

public static async void PostUploadtoCloud( List<Dictionary<string, byte[]>> _commonFileCollection)
{
    var _dickeyValuePairs = _commonFileCollection.SelectMany(x=> x).ToDictionary(x=> x.Key, x=> x.Value);
}

But beware that if they contain same keys - you will get exception.

To avoid it - you can use lookup (basically dictionary but in value it stores collection):

public static async void PostUploadtoCloud( List<Dictionary<string, byte[]>> _commonFileCollection)
{
    var _dickeyValuePairs = _commonFileCollection.SelectMany(x=> x).ToLookup(x=> x.Key, x=> x.Value); //ILookup<string, IEnumerable<byte[]>>
}

*beware that if they contain same keys - you will get exception.* - any suggestion to avoid such exception? — sujith karivelil, Aug 23 '18 at 07:03

score 1 · Answer 2 · answered Aug 23 '18 at 06:59

Try with modify loop like the following:

public static async void PostUploadtoCloud(List<Dictionary<string, byte[]>> _commonFileCollection)
{
    Dictionary<string, Byte[]> _dickeyValuePairs = new Dictionary<string, byte[]>();
    Byte[] itemData;
    foreach (var item in _commonFileCollection)
    {    
        foreach (var kvp in item)
        {
            if (!_dickeyValuePairs.TryGetValue(kvp.Key, out itemData))
            {
                _dickeyValuePairs.Add(kvp.Key, kvp.Value);
            }
        }

    }
}

Update:

The outer loop will iterate through each dictionaries in the list, where as the inner loop will iterate each items of the dictionary. The additional part _dickeyValuePairs.TryGetValue will help you to avoid exception on adding duplicate keys if any.

JohnChris · Answer 3 · 2018-08-23T07:05:24.040

You need to employ some safety in your code when doing this, a simple merge like @Pritish said wont work due to the possible exception,

public static async void PostUploadtoCloud(List<Dictionary<string, byte[]>> _commonFileCollection)
{
 Dictionary<string, Byte[]> _dickeyValuePairs = new Dictionary<string, byte[]>();
try
{
 foreach (var item in _commonFileCollection)
  {
    foreach (var kvp in item)
    {
        //you can also use TryAdd
        if(!_dickeyValuePairs.Contains(kvp.Key))
        {
            _dickeyValuePairs.Add(kvp.Key, kvp.Value);
        }
        else
        {
            //send message that it could not be done?
        }
    }

   }
 }
 catch(Exception e)
 {
  //log exception
 } 
}

How to add List object to Dictionary

3 Answers3