如何更改SQL查询左联接到LINQ查询

Question

我想将SQL Server语句更改为linq。 我是linq的初学者。 我需要在应用程序中修改linq语句，但我了解SQL语句。

这是我的SQL Server语句（对我来说结果可以）。 我想将此SQL语句更改为linq语句。

 SELECT 
    oh.OrderNo, 
    oh.PONo, 
    oh.CostCenter, 
    oh.ExpectedDeliveryDate,
    do.DeliveryDate,
    oh.PrimaryContactPerson,
    oh.AlternateContactPerson,
    oh.PrimaryContactNo,
    oh.AlternateContactNo,
    oh.CreatedDate,
    oh.CreatedDate,
    oh.WaybillNo,
    do.DeliveryStatus,
    oh.Email,
    oh.Address,
    oh.PostalCode,
    oh.City,
    oh.Branch,
    oh.DONO,
    ih.InvoiceNo,
    ih.IsPaid
FROM dbo.tbl_OrderHeader AS oh
LEFT JOIN dbo.tbl_DeliveryOrder AS do ON oh.ID = do.OrderHeaderID
LEFT JOIN dbo.tbl_InvoiceHeader AS ih ON oh.ID = ih.OrderHeaderID
LEFT JOIN Admin.tbl_UserAccount AS ua ON oh.CreatedUserID = ua.ID
LEFT JOIN Admin.tbl_UserProfile AS up ON ua.UserProfileID = up.ID
WHERE oh.Active = 1 AND up.CompanyID = '05ba4b10-79d1-4367-a5ed-077be72dae86'
ORDER BY oh.OrderNo DESC

这需要修改我的linq语句。 （结果与sql语句不同）

public IList<OHList> GetValues_Admin(Guid companyID)
    {
        IList<OHList> tblObj = null;
        try
        {

            tblObj = (from OH in _entities.tbl_OrderHeader

                  join ua in _entities.tbl_UserAccount on OH.CreatedUserID equals ua.ID
                  join up in _entities.tbl_UserProfile on ua.UserProfileID equals up.ID
                  join IH in _entities.tbl_InvoiceHeader on OH.ID equals IH.OrderHeaderID
                  join DO in _entities.tbl_DeliveryOrder on OH.ID equals DO.OrderHeaderID
                  into O                          
                  from DO in O.DefaultIfEmpty()
                  where (OH.Active == true) && (up.CompanyID == companyID)
                  orderby OH.OrderNo descending
                  select new OHList
                  {
                      OrderNo = OH.OrderNo,
                      PONo = OH.PONo,
                      CostCenter = OH.CostCenter,
                      ExpectedDeliveryDate = OH.ExpectedDeliveryDate,
                      DeliveryDate = DO.DeliveryDate,
                      PrimaryContactPerson = OH.PrimaryContactPerson ?? "",
                      AlternateContactPerson = OH.AlternateContactPerson ?? "",
                      PrimaryContactNo = OH.AlternateContactNo ?? "",
                      AlternateContactNo = OH.AlternateContactNo ?? "",
                      CreatedDate = OH.CreatedDate,
                      OrderDate = OH.CreatedDate,
                      WaybillNo = OH.WaybillNo,
                      DeliveryStatus = DO.DeliveryStatus,
                      Email = OH.Email ?? "",
                      Address = OH.Address ?? "",
                      PostalCode = OH.PostalCode ?? "",
                      City = OH.City ?? "",
                      Branch = OH.Branch,
                      DONo = DO.DONo,
                      InvoiceNo = IH.InvoiceNo ?? "",
                      IsPaid = IH.IsPaid

                  }).ToList();

    }
    catch (Exception ex)
    {
        base.Exception(ex);
    }
    return tblObj;
}

Answer 1

我将这段代码转换为Linq。
谢谢所有的建议。
从此链接引用。

 public IList<OHList> GetValues_Admin(Guid companyID)
{
IList<OHList> tblObj = null;
try
{

    tblObj = (from OH in _entities.tbl_OrderHeader
              join DO in _entities.tbl_DeliveryOrder on OH.ID equals DO.OrderHeaderID into t1
              from t11 in t1.DefaultIfEmpty()
              join IH in _entities.tbl_InvoiceHeader on OH.ID equals IH.OrderHeaderID into t2
              from t22 in t2.DefaultIfEmpty()
              join UA in _entities.tbl_UserAccount on OH.CreatedUserID equals UA.ID                          
              join UP in _entities.tbl_UserProfile on UA.UserProfileID equals UP.ID
              where (OH.Active == true) && (UP.CompanyID == companyID)
              orderby OH.OrderNo descending
              select new OHList 
              {
                  OrderNo = OH.OrderNo,
                  PONo = OH.PONo,
                  CostCenter = OH.CostCenter,
                  ExpectedDeliveryDate = OH.ExpectedDeliveryDate,
                  DeliveryDate = t11.DeliveryDate,
                  PrimaryContactPerson = OH.PrimaryContactPerson ?? "",
                  AlternateContactPerson = OH.AlternateContactPerson ?? "",
                  PrimaryContactNo = OH.AlternateContactNo ?? "",
                  AlternateContactNo = OH.AlternateContactNo ?? "",
                  CreatedDate = OH.CreatedDate,
                  OrderDate = OH.CreatedDate,
                  WaybillNo = OH.WaybillNo,
                  DeliveryStatus = t11.DeliveryStatus,
                  Email = OH.Email ?? "",
                  Address = OH.Address ?? "",
                  PostalCode = OH.PostalCode ?? "",
                  City = OH.City ?? "",
                  Branch = OH.Branch,
                  DONo = t11.DONo,
                  InvoiceNo = t22.InvoiceNo ?? "",
                  IsPaid = (t22.IsPaid == true) ? true : (bool?)null
              }).ToList();
}
catch (Exception ex)
{
    base.Exception(ex);
}
    return tblObj;
}