查询

获取查询结果的单个值：

[HttpGet("Count")]
        public async Task<ActionResult> GetCount()
        {
            using IDbConnection con = new SqlConnection(MyConfig.ConnectionString);
            string sql = "select count(*) from T_Book ";
            var count = await con.ExecuteScalarAsync(sql);// 返回dynamic类型
            return Ok(count);
        }
        [HttpGet("CountInt")]
        public async Task<ActionResult> GetCountInt()
        {
            using IDbConnection con = new SqlConnection(MyConfig.ConnectionString);
            string sql = "select count(*) from T_Book";
            int count = await con.ExecuteScalarAsync<int>(sql);//返回整形
            return Ok(count);
        }