C# Log in & connection to database

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

namespace WindowsFormsApplication_toLogIn
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btnLogIn_Click(object sender, EventArgs e)
        {
            // First create DB and table, follow copy/pase connection string
            SqlConnection cnn = new SqlConnection("Your connection string");

            // For query
            SqlDataAdapter da = new SqlDataAdapter("SELECT user, pass FROM yourTable WHERE user='" + txtUser.Text + "' and pass='" + txtPass.Text + "'", cnn);

            // fill dataset
            DataSet ds = new DataSet();
            da.Fill(ds);

            // Check trust
            if (ds.Tables["yourTable"].Rows.Count > 0)
            {
                // Log in
            }
            else
            {
                // No Log in
            }
        }
    }
}