How to Merge Array in C#

void mergeArrayExample()
    {
        string[] Arr1 = { "a", "b", "c", "d" };
        string[] Arr2 = { "d", "e", "f" };
        string[] Arr3 = { "d", "e", "f" };
        int intlength = Arr1.Length;
        int destinationIndex = Arr2.Length;

        Array.Resize(ref Arr2, Arr1.Length + Arr2.Length + Arr3.Length);
        Array.Copy(Arr1, 0, Arr2, destinationIndex, intlength);
        destinationIndex = intlength + destinationIndex;
        intlength = Arr3.Length;

        Array.Copy(Arr3, 0, Arr2, destinationIndex, intlength);
        Array.Sort(Arr2);
    }