How to convert the result of LINQ query to List

Pavel

Hello,

Here is function, that I use the list of permutations:
        public static IEnumerable> Permute(IEnumerable list)
        {
            if (list.Count() == 1)
                return new List> { list };

            return list.Select((a, i1) => Permute(
                            list.Where((b, i2) => i2 != i1)).Select(
                                    b => (new List { a }).Union(b))
                            ).SelectMany(c => c);
        }

I use it in the following way:
var SFP_vars = Permute(SFP);

Where SFP is array of bytes:
byte[] SFP = new byte[7] { 0, 1, 2, 3, 4, 5, 6 };

There is other variable:
List lst_SFP = new List();

Now my question: How to assign the value of SFP_vars to lst_SFP ?
lst_SFP = SFP_vars.ToList() doesn't work.

Thanks in advance.

Pavel.

6 Replies

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Vulpes14y ago
Accepted answer
SFP_vars is actually an IEnumerable> rather than an IEnumerable.

This means that the you first need to convert the IEnumerable objects to byte[] using the ToArray() method. You can then add them to the list.

Although it amounts to the same thing, you could replace the two lines I posted earlier with this LINQ query:

List lst_SFP = SFP_vars.Select(ie => ie.ToArray()).ToList();
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Pavel14y ago
Ok. Clear. Thanks a lot !
0
Vulpes14y ago
The looping is hidden within the ToList() method.

Without doing any actual testing, my guess would be that the second variant is slightly slower than the first because there's an extra method call, but the difference should be negligible.
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Pavel14y ago
Also works ! Is second variant more rapide than previous one ? Apparently there is no loop ...
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Pavel14y ago
Works! Thanks Vulpes.

One question (just for curiosity) - for what usage the function ToList() stands for ?
The SFP_vars is sequence of objects of type byte[]. The variable lst_SFP is the list of the objects of the same type. Why simple conversion isn't possible and therefore one need to employ a loop ?
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Vulpes14y ago
Try this:

List lst_SFP = new List();

foreach(var ie in SFP_vars) lst_SFP.Add(ie.ToArray());
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