Puedes usar LINQ:
Dim arr1 As Integer() = {1, 2, 3}
Dim arr2 As Integer() = {4, 5, 6}
Dim arr3 As Integer() = {7, 8, 9}
Dim Result As Integer() =
arr1.
Concat(arr2).
Concat(arr3).
ToArray
MsgBox(String.Join(", ", Result)) ' Result = {1, 2, 3, 4, 5, 6, 7, 8, 9}
¿Cual es el problema que tienes al concatenarlos?
Si tienes un Array puedes convertirlo/castearlo a un
Enumerable para manejar LINQ.
Dim arr1 As Array = {1, 2, 3}
Dim arr2 As Array = {4, 5, 6}
Dim arr3 As Array = {7, 8, 9}
Dim Result As Integer() =
arr1.Cast(Of Integer).
Concat(arr2.Cast(Of Integer)).
Concat(arr3.Cast(Of Integer)).
ToArray
MsgBox(String.Join(", ", Result)) ' Result = {1, 2, 3, 4, 5, 6, 7, 8, 9}
Saludos!