统计字符串中字母个数（C#程序设计）

C#程序设计：

 private void button1_Click(object sender, EventArgs e)
        {
            int[] array = new int[26];
            for (int i = 0; i < 26; i++)
                array[i] = 0;
            for (int i = 0; i < textBox1.Text.Length; i++)
            {
                if (textBox1.Text[i] >= 'a' && textBox1.Text[i] <= 'z')
                {
                    array[(int)textBox1.Text[i] - 97]++;
                }
            }
            for (int i = 0; i < 26; i++)
                textBox2.Text += ((char)(97 + i)).ToString() + ":" + array[i] + "\t";
        } private void button1_Click(obj