数组的元素在指定位置插入一个数字

  private void button1_Click(object sender, EventArgs e)
        {
            int [] num=new int[6];
            num[0] = 0;
            num[1] = 1;
            num[2] = 2;
            num[3] = 3;
            num[4] = 4;

            string res = string.Empty;
            for (int i = 0; i < num.Length; i++)
            {
                res += num[i] + ",";
            }
            this.label1.Text = "插入前："+res;

            string res1 = string.Empty;
            for (int i = 0; i < num.Length; i++)
            {
                res += num[i];
                if (i == 2)
                {

                    for (int j = num.Length-1; j > 2; j--)
                    {
                        if (j < 6) 
                        {
                            num[j] = num[j - 1];
                        }
                        
                    }
                    num[2] = int.Parse(this.textBox1.Text);
                    break;
                }
            }

            for (int i = 0; i < num.Length; i++)
            {
                res1 += num[i].ToString()+",";
            }
            this.label2.Text = "插入后：" + res1;
        }