ERROR SQL WITH C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.Sql;
using System.Data.SqlClient;

namespace Learn_App_Login
{
    public partial class Form1 : Form
    {
        //khai bao bien
        private SqlConnection InitCon;
        private SqlCommand cmd;

        public Form1()
        {
            InitializeComponent();
        }
        //ham ket noi database
        public static SqlConnection GetCon()
        {
            string strcon = @"data source=LAPTOP-AFR31CFM.;
            initial catalog ='SaleDB';
            user id='LAPTOP-AFR31CFM\D4RKDR4G0N'; password='Hacker12@#!';
            Integrated Security=true;";
            SqlConnection con = new SqlConnection(strcon);
            return con;
        }

        private void label2_Click(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            SqlConnection connectionToServer = new SqlConnection();
            SqlConnection con = GetCon();
            con.Open();
            string sqlSelect = "select * from account" +
                               "Where username ='" + txtUsername.Text + "' and password ='" + txtPassword.Text + " ' ";
            // khoi tao doi tuong command
            cmd = new SqlCommand(sqlSelect,con);
            cmd.CommandType = CommandType.Text;
            //khoi tao doi tuong adapter
            SqlDataAdapter adapter = new SqlDataAdapter(cmd);
            //tao datable chua data
            DataTable dt = new DataTable();
            //su dung adapter do data vao table nay
            adapter.Fill(dt);
            //binding eridview voi table
            dgwAccount.DataSource = dt;


        }
    }
}