Today I had to flatten a jagged array.  In my case, it was a string[][] and I needed to make sure every single string contained in that jagged array was set to something (non-null and non-empty).  LINQ made the flattening very easy.  In fact, I ended up making a generic version that I could use to flatten any type of jagged array (assuming it's a T[][]):

private static IEnumerable<T> Flatten<T>(IEnumerable<T[]> data)

{

    return from r in data from c in r select c;

}

Then, checking to make sure the data was valid, was easy:

var flattened = Flatten(data);

bool isValid = !flattened.Any(s => String.IsNullOrEmpty(s));

You could even use method grouping and reduce the validation to:

bool isValid = !flattened.Any(String.IsNullOrEmpty);