登录的两种方法

登录一般有两种方法：一种是字符串拼接的方法；另一种是参数法。

一、字符串拼接法

            SqlConnection con = new SqlConnection("Server=.;database=CESAW;Integrated Security=true;");
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandText = "Select * from UserInfo where UserName='" + textBox1.Text.Trim() + "' and UserPwd='" + textBox2.Text.Trim() + "'";

            try
            {
                con.Open();
                int i = (int)cmd.ExecuteScalar();
                if (i > 0)
                {
                    Form2 f = new Form2();
                    f.ShowDialog();
                    this.Hide();
                }
                else
                {
                    MessageBox.Show("登录失败！");
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            finally
            {
                con.Close();
            }

二、参数法

            SqlConnection con = new SqlConnection("Server=.;database=CESAW;Integrated Security=true;");
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandText = "Select * from UserInfo where UserName=@UserName and UserPwd=@UserPwd";
            SqlParameter p1 = new SqlParameter("@UserName", SqlDbType.NVarChar);
            SqlParameter p2 = new SqlParameter("@UserPwd", SqlDbType.NVarChar);
            p1.Value = textBox1.Text.Trim();
            p2.Value = textBox2.Text;
            cmd.Parameters.Add(p1);
            cmd.Parameters.Add(p2);

            try
            {
                con.Open();
                int i = (int)cmd.ExecuteScalar();
                if (i > 0)
                {
                    Form2 f = new Form2();
                    f.ShowDialog();
                    this.Hide();
                }
                else
                {
                    MessageBox.Show("登录失败！");
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            finally
            {
                con.Close();
            }