How to split an array of objects into multiple sub arrays of a given size

Question

I would like to split an array of objects into multiple array that hold no more than 10 elements.

Spent quite a while looking at examples, and the closest I can find is in C#:

Enumerable.Range(0, 100).Select((Value, Index) => new {Value, Index})
    .GroupBy(p => p.Index/10)
    .Select(g => g.Select(p => p.Value).ToList())

This runs and works in LinqPad, so I tried to convert it to VB.Net:

Enumerable.Range(0, 100).Select(Function(Value, Index) New With {Value, Index}) _
    .GroupBy(Function(x) x.Index / 10) _
    .Select(Function(g) g.Select(Function(p) p.Value).ToList())

But this doesn't give the same result, even though it looks like it should.

Obviously this is just an example and I would really like it to work on an array of customs objects. (Bonus points: why aren't these two examples equivalent?).

But this doesn't give the same result: then: what does it give? Wherein does it differ? My guess (been a long time since VB): the division results in doubles instead of integers? — RobIII
– RobIII, Commented Jul 3, 2014 at 13:27
The results are quite big, so I didn't include them to avoid clutter... it gives a hundred arrays with one item in each, — Mr Shoubs
– Mr Shoubs, Commented Jul 3, 2014 at 13:28
If you'd have taken a look at the group-key you should've seen (judging from the currently posted answers which support my hunch) that the keys are all doubles / floats instead of integers. Debugging and looking at the actual results comparing them to expected results should've saved you from posting this question ;-) — RobIII
– RobIII, Commented Jul 3, 2014 at 13:30
how would you look at the group-key, I'm new to linq, also, how can you debug linq? I haven't worked this out yet... its more of a run it and find out method. which isn't great... what is your suggestion? — Mr Shoubs
– Mr Shoubs, Commented Jul 3, 2014 at 13:31
The .Select(...) after the GroupBy() "strips" the keys from the GroupBy result so probably the easiest would be storing the intermediate results in a variable and first looking at that (like foo = Enumerable....GroupBy(...), then inspect foo with the debugger). — RobIII
– RobIII, Commented Jul 3, 2014 at 13:33

Tim Schmelter · Accepted Answer · 2014-07-03 13:35:00Z

5

In C# you have integer division which means that the decimal places are truncated and the result is also an int. That's why it works in C# and not in VB.NET which maintains decimal places since it converts it to Double.

If you want to have the same behaviour in VB.NET you need to use \ instead of /.

See: \ Operator (Visual Basic)

Enumerable.Range(0, 100).Select(Function(Value, Index) New With {Value, Index}) _
    .GroupBy(Function(x) x.Index \ 10) _
    .Select(Function(g) g.Select(Function(p) p.Value).ToList())

edited Jul 3, 2014 at 13:35

answered Jul 3, 2014 at 13:27

Tim Schmelter

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Vasistan · Accepted Answer · 2014-07-03 13:53:06Z

-1

Other wise try the below

        int currentPosition = 0;
        int maxArrayLimit = 10;

        //Total values 0-103
        List<int> lstNumbers = Enumerable.Range(0, 103).Select(x => x).ToList<int>();

        //to hold splited values 
        List<List<int>> lstSplitedNumbers = new List<List<int>>();

        while (currentPosition < lstNumbers.Count)
        {
            //spliting values based on currentPosition to maxArrayLimit
            List<int> lstCurrentNumbers = lstNumbers.Skip(currentPosition).Take(maxArrayLimit).ToList<int>();
            lstSplitedNumbers.Add(lstCurrentNumbers);
            //rest the current position
            currentPosition += lstCurrentNumbers.Count;
        }

answered Jul 3, 2014 at 13:53

Vasistan

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1 Comment

Mr Shoubs Over a year ago

Thanks, but I was looking for a linq example.

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