C# step by step

做为学习过程中的札记 所写的都是本人自己的一些设计写法 只是想记录一下学习的点点嘀嘀。
转入正题：利用数据库提取用户验证信息实现登陆。
priviate void button1_Click(object sender,System.EventArgs e)
{
       SqlConnection conn=new SqlConnection("@Data Source="(local);Integrated Security=SSPI;Initial Catalog=DBApp"");
       SqlCommand cmd=conn.CreateCommand();
       cmd.CommandType=CommandType.Text;
     cmd.CommandType = CommandType.Text;
            if (txtUserName.Text.Length == 0)
            {
                MessageBox.Show("用户不能为空，请查询后输入");
                txtPassWord.Focus();
                return;
            }
            cmd.CommandText = "select count(*) from UserList where UserName='" + txtUserName.Text + "'";
            conn.Open();
            if ((int)cmd.ExecuteScalar() == 0)
            {
                MessageBox.Show("不存在此用户，请检查后重新输入");
                txtPassWord.Focus();
                return;
            }
            cmd.CommandText = "select UserName, PassWord from UserList where PassWord='" +txtPassWord .Text + "'";
            SqlDataReader myReader = cmd.ExecuteReader();
            if (myReader.Read())
            {
                if (txtPassWord.Text == myReader[0].ToString() && txtUserName.Text.Length != 0) ;
                MessageBox.Show("登录成功", "恭喜", MessageBoxButtons.OK, MessageBoxIcon.Information);
                frmMain fm = new frmMain();
                fm.ShowDialog();
            }

            else
            {
                MessageBox.Show("用户" + txtUserName.Text + "的密码不正确", "密码", MessageBoxButtons.OKCancel, MessageBoxIcon.Warning);
                txtPassWord.Focus();
                return;
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Close();
        }
}