Converting a string array to an integer array

you can use LINQ:

var ints = code.SelectMany(s => s.Split(' ')).Select(int.Parse).ToList();

This will take your list of space-separated numbers and flatten them into a one-dimensional List of ints

var intArray =  File.ReadAllText(@"C:\randoms\randnum.txt")
        .Split((char[]) null, StringSplitOptions.RemoveEmptyEntries)
        .Select(int.Parse).ToArray();

Some of these answers are great, but if your file contains any strings that can't be converted to an int, int.Parse() will throw an exception.

Although slightly more expensive, consider doing a TryParse instead. This gives you some Exception handling:

int tmp = 0; // Used to hold the int if TryParse succeeds

int[] intsFromFile = System.IO.File
        .ReadAllText(@"C:\randoms\randnum.txt")
        .Split(null)
        .Where(i => int.TryParse(i, out tmp))
        .Select(i => tmp)
        .ToArray();

It's a one-liner, really. This will give you a 1-dimensional array of integers in the file:

private static rxInteger rxInteger = new Regex(@"-?\d+") ;

...

int[] myIntegers1 = rxInteger
                    .Matches( File.ReadAllText(@"C:\foo\bar\bazbat") )
                    .Cast<Match>()
                    .Select( m => int.Parse(m.Value) )
                    .ToArray()
                    ;

If you want it to be a 2-dimensional ragged array, it's not much more complicated:

int[][] myIntegers2 = File
                      .ReadAllLines( @"C:\foo\bar\bazbat" )
                      .Select( s =>
                        rxInteger
                        .Matches(s)
                        .Cast<Match>()
                        .Select( m => int.Parse(m.Value) )
                        .ToArray()
                      )
                      .ToArray()
                      ;

[implementation of validation and error handling left as an exercise for the reader]

At first glance, it appears the problem is that you're reading in numbers using ReadAllLines. This will return an array of strings where each string represents one line in your file. In your example it appears that your numbers are all on one line. You could use System.IO.File.ReadAllText to get a single string. Then use .Split(new char[]{}, StringSplitOptions.RemoveEmptyEntries); to get the array of strings your looking for.

string allTheText = System.IO.File.ReadAllText(@"C:\randoms\randnum.txt");
string[] numbers = allTheText.Split(new char[]{}, StringSplitOptions.RemoveEmptyEntries);