C#合并字符串数组

string[] hidenumber = HiddenField1.Value.Split(',');
            string[] phonenumber = txtPhoneNum.Text.Trim().Split('\r');

            string[] moble = new string[hidenumber.Length + phonenumber.Length];

            int index = 0;
            for (int i = 0; i < hidenumber.Length; i++) {
                moble[index] = hidenumber[i];
                index++;
            }

            for (int j = 0; j < phonenumber.Length; j++) {
                moble[index] = phonenumber[j];
                index++;
            }