Dictionary in C# with list of Int[] values not displaying

Question

I am trying to display the values from a dictionary function but it does not display the value, what it shows is below -

1007 System.Collections.Generic.List`1[System.Int32[]] 

1006 System.Collections.Generic.List`1[System.Int32[]] 

1009 System.Collections.Generic.List`1[System.Int32[]] 

1008 System.Collections.Generic.List`1[System.Int32[]]

the code I am using is shown below

    clsCollaborativeFilter mri = new clsCollaborativeFilter();
    Dictionary<int, List<int[]>> movRecommendations = mri.aList1();

    foreach (KeyValuePair<int, List<int[]>> kvp in movRecommendations)
    {
        da.Text += kvp.Key;
        da.Text += " ";
        da.Text += kvp.Value;
        da.Text += "<br/>";
    }
    return da.Text;

I cant seem to understand why this is happening

Well, you're calling ToString() on a List<int[]>. How were you expecting that to perform a conversion, and why? (I'd strongly recommend building all the text in a StringBuilder first, and then setting da.Text at the end, btw.) — Jon Skeet
– Jon Skeet, Commented Aug 11, 2015 at 17:40
Related: Question regarding C#'s List<>.ToString, but I'm pretty sure this is a duplicate of something out there. — crashmstr
– crashmstr, Commented Aug 11, 2015 at 17:54
System.Collections.Generic.List`1System.String issue in mvc4 — crashmstr
– crashmstr, Commented Aug 11, 2015 at 17:57

maraaaaaaaa · Accepted Answer · 2015-08-11 17:45:20Z

1

you are adding a List of an Array of ints to a string, in the line: da.Text += kvp.Value; so what it is doing, is it is adding the signature of the List of Arrays because it doesn't know exactly what you are trying to do.

What you can do instead is:

da.Text += String.Join(", ", kvp.Value.SelectMany(i => i));

answered Aug 11, 2015 at 17:45

maraaaaaaaa

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1 Comment

Mr_Malone86 Over a year ago

yea that seem to work now I am able to see the values I required so thanks

Dai · Accepted Answer · 2015-08-11 19:37:48Z

1

...or assuming that it really is a dictionary-of-list-of-int-arrays, then:

StringBuilder sb = new StringBuilder();
foreach(Int32 key in movRecommendations.Key) {
    List<Int32[]> listOfArrays = movRecommendations[ key ];

    sb.Append( key );
    sb.AppendLine();
    foreach(Int32[] array in listOfArrays) {
        Boolean isFirst = true;
        foreach(Int32 val in array) {
            if( !isFirst ) sb.Append( ", " );
            sb.Append( val );
            isFirst = false;
        }
        sb.AppendLine();
    }
    sb.AppendLine("<br />");
}
da.Text = sb.ToString();

edited Aug 11, 2015 at 19:37

answered Aug 11, 2015 at 17:45

Dai

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Comments

Dai · Accepted Answer · 2015-08-11 17:42:46Z

0

I think what you actually want is this:

Dictionary< int, List<int> >

...a List<int[]> doesn't make much sense to me.

answered Aug 11, 2015 at 17:42

Dai

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Piotr Dory · Accepted Answer · 2015-08-11 17:44:16Z

0

clsCollaborativeFilter mri = new clsCollaborativeFilter();
Dictionary<int, List<int[]>> movRecommendations = mri.aList1();

foreach (KeyValuePair<int, List<int[]>> kvp in movRecommendations)
{
    da.Text += kvp.Key;
    da.Text += " ";
    da.Text += string.Join(",",kvp.Value);
    da.Text += "<br/>";
}
return da.Text;

answered Aug 11, 2015 at 17:44

Piotr Dory

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3 Comments

Piotr Dory Over a year ago

Oh true, as Dai posted, you are making dictionary of lists of arrays of ints

maraaaaaaaa Over a year ago

This will still print the signature of the arrays, because kvp.Value is a list of Arrays, what you need instead is to flatten the ints by doing kvp.Value.SelectMany(i => i)

Piotr Dory Over a year ago

Yeah I noticed that it is Dictionary<int, List<int[]>>, not Dictionary<int, List<int>>. Well, there are already other answers which will work

Mister Epic · Accepted Answer · 2015-08-11 17:53:59Z

0

Dictionary<int, List<int[]>> movRecommendations = new Dictionary<int, List<int[]>>(){
    {0, new List<int[]>(){ new int[]{1, 2, 3} }},
    {1, new List<int[]>(){ new int[]{7, 8, 9} }}
};
string da = String.Empty; 
foreach (KeyValuePair<int, List<int[]>> kvp in movRecommendations)
{
    da += kvp.Key;
    da += " ";
    da += String.Join(", ", kvp.Value.SelectMany(i => i));
    da += "<br/>";
}
Console.WriteLine (da);

This will write out 0 1, 2, 3<br/>1 7, 8, 9<br/>

answered Aug 11, 2015 at 17:53

Mister Epic

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