1. 来张 效果图 （简陋的界面 凑合着看吧）

2. 代码

 private void button1_Click(object sender, EventArgs e)
        {
            string sin = txtsid.Text;
            int alpha = 0;
            int num = 0;
            int spc = 0;
            for (int i = 0; i < sin.Length; i++)
            {
                string ch = sin.Substring(i, 1);
                if (ch == " ")
                    spc += 1;
                else if (char.IsNumber(ch, 0))
                {
                    num += 1;
                }
                else if (char.IsUpper(ch, 0) | char.IsLower(ch, 0))
                {
                    alpha += 1;
                }

            }
            MessageBox.Show("空格=" + spc + ",数字=" + num + ",字母=" + alpha);

        }