int[] arr = new int[] { 0x11, 0x02, 0x03, 0xff };
            string s = "";
            foreach (int i in arr)
            {
                s += Convert.ToString(i, 16).PadLeft(2,'0');
            }
            MessageBox.Show(s);

------解决方案--------------------
C# code

byte[] arr = new byte[1024];
arr[0] = 0x11;
arr[1] = 0x02;
arr[2] = 0x03;
arr[3] = 0xff;

string s = "";
for (int i = 0; i < arr.Length && arr[i] > 0; i++)
{
    s += arr[i].ToString("x2");
}
或者
string s = string.Join("", Array.ConvertAll(Array.FindAll(arr, o => o > 0), o => o.ToString("x2")));