左连接Linq到实体'；s Vb.net

我无法理解linq到实体查询的语法。我的问题是，如果Calls表的值为null，那么就不会出现任何问题，我希望进行类似于左连接的操作，以从Calls表中获取“all”行

我试着把它分组，但我想不出正确的写作方法

Dim TicketQuery As ObjectQuery = From c In EnData.Customer _
                                         Join t In EnData.Calls On t.CustomerID Equals c.CustomerID _
                                         Join Status In EnData.Lists On t.Status Equals Status.ListValue _
                                         Join Project In EnData.Lists On t.Project Equals Project.ListValue _
                                         Join Priorty In EnData.Lists On t.Priority Equals Priorty.ListValue _
                                         Where c.Status > -1 And t.Status > -1 And Status.ListType = 1 And Project.ListType = 3 And Priorty.ListType = 2 _
         Select New With {c.CustName, t.CallID, t.CallDate, t.CallTime, t.Description, Key .Status = Status.ListText, Key .Project = Project.ListText, t.DateModified, Key .Priority = Priorty.ListText}

我如何解决这个问题？

类似的问题：

Microsoft文档：

LINQ示例来自：

左外连接 所谓的外部联接可以用组联接来表示。左侧外部连接类似于交叉连接，只是所有左侧元素至少包含一次，即使它们与任何右侧元素都不匹配。注意蔬菜是如何显示在输出中的，即使它没有匹配的产品

Public Sub Linq105()
    Dim categories() = {"Beverages", "Condiments", "Vegetables", "Dairy Products", "Seafood"}

Dim productList = GetProductList()

Dim query = From c In categories _
            Group Join p In productList On c Equals p.Category Into Group _
            From p In Group.DefaultIfEmpty() _
            Select Category = c, ProductName = If(p Is Nothing, "(No products)", p.ProductName)

For Each v In query
    Console.WriteLine(v.ProductName + ": " + v.Category)
Next
End Sub

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对于VB.net中的左连接，我们可以使用Let

Dim q = 
    (From item In _userProfileRepository.Table
     Let Country = (From p In _countryRepository.Table Where p.CountryId = item.CurrentLocationCountry Select p.Name).FirstOrDefault
     Let State = (From p In _stateRepository.Table Where p.CountryId = item.CurrentLocationCountry Select p.Name).FirstOrDefault
     Let City = (From p In _stateRepository.Table Where p.CountryId = item.CurrentLocationCountry Select p.Name).FirstOrDefault
    Where item.UserId = item.ProfileId.ToString)

在左连接之后，我们可以使用GROUPBY

Dim q2 = 
    (From p In q Group p By p.Country, p.State, p.City Into Group 
     Select New With 
         {
             .Country = Country, 
             .State = State, 
             .City = City, 
             .Count = Group.Count
         }).ToList()

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你能解释一下你想看到的结果吗？如果你创建了虚拟类，你可以在LINQPad中测试你的LINQ