My first C# code

using System;
using System.Collections.Generic;
using MySql.Data.MySqlClient;

/// <summary>
/// Global database class contains general database functions
/// </summary>
public class Database
{
    private string connstr = "Server=localhost;database=msg;user=root;pass=Ly@12157114";

    public MySqlDataReader GetReader(String sql, List<MySqlParameter> args)
    {
        MySqlConnection conn = new MySqlConnection(connstr);
        MySqlCommand cmd = new MySqlCommand(sql, conn);

        if (args.Count != 0)
        {
            cmd.Parameters.AddRange(args.ToArray());
        }

        MySqlDataReader dr = cmd.ExecuteReader();
        return dr;
    }

    public void DoCommand(string sql, List<MySqlParameter> args)
    {
        MySqlConnection conn = new MySqlConnection(connstr);
        MySqlCommand cmd = new MySqlCommand(sql, conn);

        if (args.Count != 0)
        {
            cmd.Parameters.AddRange(args.ToArray());
        }

        conn.Open();
        cmd.ExecuteNonQuery();
        conn.Close();
    }
}

using System;
using System.Collections.Generic;
using MySql.Data.MySqlClient;

public partial class Login : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void btnLogin_Click(object sender, EventArgs e)
    {
        Database db = new Database();

        string sql = "select * from users where email = @email and passcode = @pass";

        List<MySqlParameter> args = new List<MySqlParameter>();
        args.Add(new MySqlParameter("@email", txtEmail.Text));
        args.Add(new MySqlParameter("@pass", txtPass.Text));

        MySqlDataReader dr = db.GetReader(sql, args);

        if (dr.HasRows)
        {
            while (dr.Read())
            {
                Session["userid"] = "{0}";
                Response.Redirect("Inbox.aspx");
            }
        }
        else
        {
            lblerr.Text = "Invalid username/password";
        }
    }
}