Comparing Two Arrays With Different Dimensions

I am trying to compare two arrays that always have different dimensions.
e.g. arr1 -> {1,2,3} and arr2->{1,2}

I did try and able to get the matching items to new array. But I am expecting to get the unmatched items only. I am expecting to compare both arrays and put only the item '3' to a new array which is in arr1 and not in arr2
e.g. arr1 -> {1,2,3} and arr2->{1,2} should result a new array with 3
arr1 -> {1,2,3,4} and arr2->{1,2} should result a array with 3,4
Is there any way of doing this for older version of .net framework without using Enumerable.Except