SqlHelper類

public static class SqlHelper
    {
        //連線字串
        private static readonly string connStr = ConfigurationManager.ConnectionStrings["mssql"].ConnectionString;


        //1.執行增、刪、改的方法：ExecuteNonQuery
        public static int ExecuteNonQuery(string sql, params SqlParameter[] pms)
        {
            using (SqlConnection con = new SqlConnection(connStr))
            {
                using (SqlCommand cmd = new SqlCommand(sql, con))
                {
                    if (pms != null)
                    {
                        cmd.Parameters.AddRange(pms);
                    }
                    con.Open();
                    return cmd.ExecuteNonQuery();
                }
            }
        }

        //2.封裝一個執行返回單個物件的方法：ExecuteScalar()
        public static object ExecuteScalar(string sql, params SqlParameter[] pms)
        {
            using (SqlConnection con = new SqlConnection(connStr))
            {
                using (SqlCommand cmd = new SqlCommand(sql, con))
                {
                    if (pms != null)
                    {
                        cmd.Parameters.AddRange(pms);
                    }
                    con.Open();
                    return cmd.ExecuteScalar();
                }
            }
        }


        //3.執行查詢多行多列的資料的方法：ExecuteReader
        public static SqlDataReader ExecuteReader(string sql, params SqlParameter[] pms)
        {
            SqlConnection con = new SqlConnection(connStr);
            using (SqlCommand cmd = new SqlCommand(sql, con))
            {
                if (pms != null)
                {
                    cmd.Parameters.AddRange(pms);
                }
                try
                {
                    con.Open();
                    return cmd.ExecuteReader(CommandBehavior.CloseConnection);
                }
                catch (Exception)
                {
                    con.Close();
                    con.Dispose();
                    throw;
                }
            }
        }


        //4.執行返回DataTable的方法
        public static DataTable ExecuteDataTable(string sql, params SqlParameter[] pms)
        {
            DataTable dt = new DataTable();
            using (SqlDataAdapter adapter = new SqlDataAdapter(sql, connStr))
            {
                if (pms != null)
                {
                    adapter.SelectCommand.Parameters.AddRange(pms);
                }
                adapter.Fill(dt);
            }
            return dt;
        }
    }
 

WinForm下登陸按鈕實現：

        //實現登入
        private void button1_Click(object sender, EventArgs e)
        {
            //1.採集使用者輸入
            var loginId = txtLoginID.Text.Trim();
            var password = txtLoginPassword.Text;

            //2.構建SQL語句
            string sql = "select count(*) from users where 
 
[email protected] and [email protected]";
            //構建引數
            SqlParameter[] pms = new SqlParameter[]
            {
                new SqlParameter("@loginId",SqlDbType.VarChar,50){ Value =loginId},
                new SqlParameter("@pwd",SqlDbType.VarChar,50){ Value =password},
            };

            //3.執行SQL語句
            // int r = (int)SqlHelper.ExecuteScalar(sql, pms);
            int r = Convert.ToInt32(SqlHelper.ExecuteScalar(sql, pms));
            //4.根據SQL語句執行結果，判斷使用者登入是否成功！
            if (r > 0)
            {
                MessageBox.Show("登入成功！");
            }
            else
            {
                MessageBox.Show("登入失敗！");
            }
        }