//取符合条件的第一个值：FirstOrDefault()
 var orderSn = _DataBase.OrderHead.Where(p => p.OrderSn.ToLower() == reqdata.Body.OrderSN.ToLower() &&  p.AppId == appid).ToList().FirstOrDefault();
//从数据库中取配置值
var ary = new string[]
                {
                        "aa:appid",
                        "aa:appkey",
                        "aa:socancel:url"                                
                };
var settings = _DataBase.BaseSetting.Where(p => p.AppId == $"{reqdata.Body.whse}" && ary.Contains(p.KeyName))
               .ToDictionary(l => l.KeyName, l => l.KeyValue);//这是结果
var settings = _Database.BaseSetting.Where(l => l.AppId == $"{_WareHouse}" && (l.KeyName == "KeyName" || l.KeyName == "KeyName2" || l.KeyName == "KeyName3")).ToList();
//两种写法
string appid = settings["aa:appid"];
string appid= settings.Where(l => l.KeyName == "aa:appid").FirstOrDefault().KeyValue;

//排序
//倒序取出最新的一个记录bid(OrderByDescending:降序)
var bid = _Database.inventory.Where(p => p.Whse == whse).OrderByDescending(l => l.BatchId).Take(1).FirstOrDefault();
var invs = _Database.inventory.Where(p => p.BatchId == bid.BatchId && p.Whse == whse && p.SyncStatus == 0).OrderBy(l => l.CreateDateTime).ToList();
关于linq的降序升序这个文档将的很好

Linq排序方式与Lambda排序方式比较以及OrderBy、ThenBy的使用

//LINQ TO XML
private JObject GenerateDelivery(Guid headid, string erpno, string ordersn, string source)
        {
            var j = new JArray((   from sns in Database.SerialNumber.Where(l => l.PkEcorderHead == headid)
                                    join o in ECDatabase.orderHead.Where(l => l.PkEcorderHead == headid)
                                     on sns.PkEcorderHead equals o.PkEcorderHead
                                    join d in ECDatabase.OmsEcorderDelivery.Where(l => l.PkEcorderHead == headid)
                                      on sns.PkEcorderHead equals d.PkEcorderHead
                                    select new
                                    {
                                       DeliveryDateTime = d.DeliveryDateTime.ToString("yyyy-MM-dd hh:mm:ss"),
                                       DeliveryNumber = d.DeliveryNumber,
                                       SerialNumber = sns.SerialNumber,
                                       Sku = sns.Sku,
                                    }
                        ) 
                               .Distinct().ToList().Select(l => new JObject(
                                                new JProperty("@tracking_time", l.DeliveryDateTime),
                                                new JProperty("@tracking_number", l.DeliveryNumber),
                                                new JProperty("@serial_number", l.SerialNumber),
                                                new JProperty("@part_no", l.Sku),
                                               )));


            var rss = new JObject
            {
                {"?xml",new JObject
                    {
                        {"@version","1.0" },
                        {"@encoding","utf-8"}
                    }
                },
                { "order", new JObject
                    {
                        {"@CO", source },
                        {"sns", new JObject
                        {
                            {"sn", j }
                        }
                        }
                    }
                }
            };
            return rss;
        }

//LINQ TO JSON

var detail = _Database.orderDetail.Where(l => l.PkEcorderHead == _HeadId).ToList();
if (detail.Count() == 0)
    throw new Exception($"AddSOToWMS:单身错误, 笔数为0");
var jary = new JArray(detail.Select(l => new JObject
                {
                    new JProperty("lineno", l.LineNum.ToString()),
                    new JProperty("goodsname", l.GoodsName),
                    new JProperty("goodsnumber", l.GoodsNumber),
                    new JProperty("partno", l.PartNo)
                }));
var obj = new JObject
                {
                    {"head", new JObject
                        {
                            { "transmessage","" },
                            { "transcode",TransCode },
                            { "transid", TransId },
                            { "errorcode", "" }
                        }
                    },
                    {"body", new JObject
                        {                            
                            { "invoicetitle", head.InvoiceTitle },
                            { "detail", jary} 
                        }
                    }
                };

标签：JProperty,JObject,写法,lamdba,Linq,var,new,PkEcorderHead,Where
来源： https://www.cnblogs.com/ZkbFighting/p/14023140.html