Cannot use the output of LINQ query

Question

Hello The initial task is to find all permutations of the byte array. byte [] SFP = new byte [8] { 0 1 2 3 4 5 6 7 }; I've found on some forum the following procedure: public static IEnumerable IEnumerable > Permute ( IEnumerable list) { if (list.Count() == 1) return new List IEnumerable > { 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 this way: var SFP_vars = Permute(SFP); It works fine - the query find all combinations. T he problem is that I can't use foreach to have access to particular memberes of list. The foreach loop (see below) provoke the runtime error: InvalidCastException was unhandled. Unable to cast object of type ' d__88`1[System.Byte]' to type 'System.Byte[]' Construction that give error: foreach ( byte [] SFP_var in SFP_vars) { } How to circumvent the problem. Thanks in advance. Pavel.

Vulpes · Answer

OK in that case we can simplify it to this: byte [] SFP = new byte[8] { 0 1 2 3 4 5 6 7 }; var SFP_vars = Permute(SFP); foreach (var SFP_var in SFP_vars) { SomeMethod(SFP_var.ToArray()); }

Vulpes · Answer

Try this: byte [] SFP = new byte[8] { 0 1 2 3 4 5 6 7 }; var SFP_vars = Permute(SFP); List list = new List (); foreach (var SFP_var in SFP_vars) { list.Add(SFP_var.ToArray()); } // print out first 20 say int count = 0; foreach(byte[] ba in list) { foreach(byte b in ba) Console.Write({0}  b); Console.WriteLine(); count++; if (count == 20) break; }

Pavel · Answer

The BEST !!! Works. Thanks Vulpes.

Pavel · Answer

Not exactly. Inside of foreach I call another function where the value of a particular SFP_var is passed as parameter. In that another function the parameter corresponding to SFP_var is declared as byte[].

Vulpes · Answer

Sure if you're just interested in iteration you could do this: byte [] SFP = new byte[8] { 0 1 2 3 4 5 6 7 }; var SFP_vars = Permute(SFP); int count = 0; foreach (var SFP_var in SFP_vars) { foreach(byte b in SFP_var) Console.Write({0}  b); Console.WriteLine(); count++; if (count == 20) break; } In practice of course you might not need the code to restrict iteration to 20 (or whatever) permutations if you're printing to a file or doing some other type of processing which doesn't involve printing to the console.

Pavel · Answer

Hi Vulpes Your solution works. Thanks. Probaably my collection declaration (byte[]) isn't optimal - because it implies using additional loop (forming list). Is there some shorter solution ? Regards. Pavel.