I am having some issues with trying to figure out the correct way, or syntax, to join/concatenate a series of "name" columns from a separate table into a query.
Currently I am testing in LINQpad using two queries; the first returns all the master data that I use for other background work, and the second is a user-friendly version that I bind to a DGV. The issue comes in when I try to join the Physicians names like I do for a separate combobox.
This is what I have thus far - while it does return the Physician's name, it will NOT return the name if the TITLE field is NULL on the Physicians table.
Dim query1 = (From demog In data_Demogs
From MedHist In data_Demog_MedHists.where(Function(a) demog.ID_Demog = a.ID_Demog).defaultifempty
From BGLAssay In data_Demog_BGLs.where(Function(a) demog.ID_Demog = a.ID_Demog).defaultifempty
Select
demog.ID_Demog,
demog.Last_Name,
demog.First_Name,
demog.ID_Demog_AKA,
demog.DOB,
demog.Gender,
demog.ST_Complete,
demog.LT_Complete,
demog.LT_Due_Date,
demog.ID_Physician,
demog.ID_Reason_For_Call,
demog.Intl_Patient,
demog.Mayo_Patient,
MedHist.ID_Disease_Group,
MedHist.ID_Disease_Type,
BGLAssay.ID_BGL_Assay)
Dim query2 = (From items In query1
From demogAKA In data_Demogs.Where(Function(a) items.ID_Demog = a.ID_Demog_AKA).defaultifempty
From DType In tbl_Disease_Types.Where(Function(a) items.ID_Disease_Type = a.ID_Disease_Type).defaultifempty
From DGroup In tbl_Disease_Groups.Where(Function(a) items.ID_Disease_Group = a.ID_Disease_Group).defaultifempty
From RFC In tbl_Reason_For_Calls.Where(Function(a) items.ID_Reason_For_Call = a.ID_Reason_For_Call).defaultifempty
From Phys In tbl_Physicians.Where(Function(a) items.ID_Physician = a.ID_Physician).defaultifempty
From Title In tbl_Titles.Where(Function(a) Phys.ID_Title = a.ID_Title).defaultifempty
Select
items.ID_Demog,
items.Last_Name,
items.First_Name,
AKA_Name = demogAKA.Last_Name + ", " + demogAKA.First_Name,
items.DOB,
items.Gender,
items.ST_Complete,
items.LT_Complete,
items.LT_Due_Date,
DType.Disease_Type_Abr,
DGroup.Disease_Group_Name,
RFC.Reason_For_Call,
items.ID_Physician,
Phys_Name = Phys.Last_Name + ", " + Phys.First_Name + ", " + Title.Title
).distinct
console.writeline(Query2)
This is the currently query I for a combobox that DOES bring back all names, joining those names even if a field is NULL.
Dim Phys = (From e In tbl_Physicians
Group Join f In tbl_Titles On e.ID_Title Equals f.ID_Title
Into Matched = Group
From m In Matched.DefaultIfEmpty()
Select e.ID_Physician,
e.Last_Name,
e.First_Name,
e.Middle_Initial,
m.Title
).ToArray().Select(Function(item) New With {
.ID = item.ID_Physician,
.Phys_Name = (String.Join(", ",
String.Join(",",
New String() {item.Last_Name, item.First_Name, item.Title}).Split(
New Char() {","}, System.StringSplitOptions.RemoveEmptyEntries)))
})
Console.writeline(Phys)
When I try to add a third query to return just the Physician's name, and join that to the final query, I get the following error:
Local sequence cannot be used in LINQ to SQL implementations of query operators except the Contains operator.
'Query 1 removed to save space
Dim PhysNames = (From e In tbl_Physicians
Group Join f In tbl_Titles On e.ID_Title Equals f.ID_Title
Into Matched = Group
From m In Matched.DefaultIfEmpty()
Select e.ID_Physician,
e.Last_Name,
e.First_Name,
e.Middle_Initial,
m.Title
).ToArray().Select(Function(item) New With {
.ID = item.ID_Physician,
.Phys_Name = (String.Join(", ",
String.Join(",",
New String() {item.Last_Name, item.First_Name, item.Title}).Split(
New Char() {","}, System.StringSplitOptions.RemoveEmptyEntries)))
})
Dim query2 = (From items In query1
From demogAKA In data_Demogs.Where(Function(a) items.ID_Demog = a.ID_Demog_AKA).defaultifempty
From DType In tbl_Disease_Types.Where(Function(a) items.ID_Disease_Type = a.ID_Disease_Type).defaultifempty
From DGroup In tbl_Disease_Groups.Where(Function(a) items.ID_Disease_Group = a.ID_Disease_Group).defaultifempty
From RFC In tbl_Reason_For_Calls.Where(Function(a) items.ID_Reason_For_Call = a.ID_Reason_For_Call).defaultifempty
From Phys In PhysNames.Where(Function(a) items.ID_Physician = a.ID).defaultifempty
Select
items.ID_Demog,
items.Last_Name,
items.First_Name,
AKA_Name = demogAKA.Last_Name + ", " + demogAKA.First_Name,
items.DOB,
items.Gender,
items.ST_Complete,
items.LT_Complete,
items.LT_Due_Date,
DType.Disease_Type_Abr,
DGroup.Disease_Group_Name,
RFC.Reason_For_Call,
items.ID_Physician,
Phys.Phys_Name
).distinct
console.writeline(Query2)
When I try to join my working query into the final query, I get the following error:
Invalid cast from 'System.String' to 'VB$AnonymousDelegate_0`2[[System.Object, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934...
'Query1 removed to save space
Dim query2 = (From items In query1
From demogAKA In data_Demogs.Where(Function(a) items.ID_Demog = a.ID_Demog_AKA).defaultifempty
From DType In tbl_Disease_Types.Where(Function(a) items.ID_Disease_Type = a.ID_Disease_Type).defaultifempty
From DGroup In tbl_Disease_Groups.Where(Function(a) items.ID_Disease_Group = a.ID_Disease_Group).defaultifempty
From RFC In tbl_Reason_For_Calls.Where(Function(a) items.ID_Reason_For_Call = a.ID_Reason_For_Call).defaultifempty
From Phys In tbl_Physicians
Where items.ID_Physician = Phys.ID_Physician
Group Join f In tbl_Titles On Phys.ID_Title Equals f.ID_Title
Into Matched = Group
From m In Matched.DefaultIfEmpty()
Select
items.ID_Demog,
items.Last_Name,
items.First_Name,
AKA_Name = demogAKA.Last_Name + ", " + demogAKA.First_Name,
items.DOB,
items.Gender,
items.ST_Complete,
items.LT_Complete,
items.LT_Due_Date,
DType.Disease_Type_Abr,
DGroup.Disease_Group_Name,
RFC.Reason_For_Call,
items.ID_Physician,
PhysName = Function(a) String.Join(", ",
String.Join(",",
New String() {Phys.Last_Name, Phys.First_Name, m.Title}).Split(
New Char() {","}, System.StringSplitOptions.RemoveEmptyEntries))
).distinct
console.writeline(Query2)
After a long time playing around in LINQpad, and then finally re-reading JM's answer to a former question I had, I realized what I was doing wrong.
As per his post:
The problem is that, while LINQ in general has no issue with that code, LINQ to Entities does. LINQ syntax is the same for every provider but the implementation under the hood differs and, in the case of LINQ to Entities, your LINQ code has to translated to SQL and, in this case, there's no mapping from String.Join to SQL. That code would work fine with LINQ to Objects so one solution is to push that operation out of the original query and into a LINQ to Objects query. That would mean selecting the raw data with your LINQ to Entities query, calling ToList or ToArray on the result to materialise the query, then performing another query on that result. That second query will be LINQ to Objects rather than LINQ to Entities and so String.Join will not be an issue.
So... Once I realized I needed to push out the String.Join, I ended up with the following code:
Dim DispList = (From items In MastList
From demogAKA In dbACL.data_Demog.Where(Function(a) items.ID_Demog = a.ID_Demog_AKA).DefaultIfEmpty
From DType In dbACL.tbl_Disease_Type.Where(Function(a) items.ID_Disease_Type = a.ID_Disease_Type).DefaultIfEmpty
From DGroup In dbACL.tbl_Disease_Group.Where(Function(a) items.ID_Disease_Group = a.ID_Disease_Group).DefaultIfEmpty
From RFC In dbACL.tbl_Reason_For_Call.Where(Function(a) items.ID_Reason_For_Call = a.ID_Reason_For_Call).DefaultIfEmpty
From e In dbACL.tbl_Physician.Where(Function(a) items.ID_Physician = a.ID_Physician).DefaultIfEmpty
Group Join f In dbACL.tbl_Title On e.ID_Title Equals f.ID_Title
Into Matched = Group
From m In Matched.DefaultIfEmpty()
Select
items.ID_Demog,
items.Last_Name,
items.First_Name,
AKALname = demogAKA.Last_Name,
AKAFname = demogAKA.First_Name,
items.DOB,
items.Gender,
items.ST_Complete,
items.LT_Complete,
items.LT_Due_Date,
DType.Disease_Type_Abr,
DGroup.Disease_Group_Name,
RFC.Reason_For_Call,
items.ID_Physician,
PLName = e.Last_Name,
PFname = e.First_Name,
PMI = e.Middle_Initial,
PTitle = m.Title
).Distinct.ToList().Select(Function(a) New With {
a.ID_Demog,
a.Last_Name,
a.First_Name,
.AKA_Name = (String.Join(", ",
String.Join(",",
New String() {a.AKALname, a.AKAFname}).Split(
New Char() {","}, System.StringSplitOptions.RemoveEmptyEntries))),
a.DOB,
a.Gender,
a.ST_Complete,
a.LT_Complete,
a.LT_Due_Date,
a.Disease_Type_Abr,
a.Disease_Group_Name,
a.Reason_For_Call,
a.ID_Physician,
.PName = (String.Join(", ",
String.Join(",",
New String() {a.PLName, a.PFname, a.PTitle}).Split(
New Char() {","}, System.StringSplitOptions.RemoveEmptyEntries)))
}).ToList()
I am successfully using some linq to populate some variables but in order to make it more efficient I would like to avoid the current repetition when setting the variables nextMDTID, nextPatientID, nextCareID and nextMDTDate.
Can I create a variable to hold the data generated using the linq query and then re-use it to avoid the repetition?
Dim thisPTOrder = (From p In ThisMDTData Where p.MDTID = Request.QueryString("MDTID") Select p.PTOrder).FirstOrDefault
Dim nextPTOrder = thisPTOrder + 1
Dim d = ThisMDTData.Where(Function(p) p.PTOrder = nextPTOrder And p.PTOrder <= p.PTOrder)
Dim nextMDTID = (From p In ThisMDTData Where p.PTOrder = nextPTOrder And p.PTOrder <= p.MaxPTOrder Select p.MDTID).FirstOrDefault
Dim nextPatientID = (From p In ThisMDTData Where p.PTOrder = nextPTOrder And p.PTOrder <= p.MaxPTOrder Select p.PatientID).FirstOrDefault
Dim nextCareID = (From p In ThisMDTData Where p.PTOrder = nextPTOrder And p.PTOrder <= p.MaxPTOrder Select p.CareID).FirstOrDefault
Dim nextMDTDate = (From p In ThisMDTData Where p.PTOrder = nextPTOrder And p.PTOrder <= p.MaxPTOrder Select p.MDTDate).FirstOrDefault
Using a proper definition for d, you can simplify the results extraction:
Dim d = ThisMDTData.Where(Function(p) p.PTOrder = nextPTOrder And p.PTOrder <= p.MaxPTOrder).Select(Function(p) New With { p.MDTID, p.PatientID, p.CareID, p.MDTDate }).FirstOrDefault
Dim nextMDTID = d?.MDTID
Dim nextPatientID = d?.PatientID
Dim nextCareID = d?.CareID
Dim nextMDTDate = d?.MDTDate
Putting the Select/FirstOrDefault on the definition of d ensures that any database is only queried once for the minimally needed data. You could leave the Select off if the row size is small, or the row only has those four properties. You can use the obvious fluent query translation for d if desired.
NOTE: If you don't want some of the variables to be Nullable, use If:
Dim nextPatientID = If(d?.PatientID, CType(Nothing, Integer))
I have 2 tables: pob (with results of some activities) and names (with user data). I try to select top 5 users from table pob based on their last activity date. So I inner join names and pob, then select top 5 users based on calculated max(date).
This query is working:
SELECT TOP 5
[u].[id],
[u].[name],
max([p].[date]) As LastDateOfUse,
FROM
[pob] [p]
INNER JOIN
[users] [u]
ON
[p].[id_name] = [u].[id]
WHERE
[p].[date] >= #2017-01-01#
GROUP BY
[u].[id],
[u].[name]
ORDER BY
max([p].[date]) DESC
Now I need to transform it into Linq query. This my attempt but it's not working.
"Key" is not a member of type "System.Collections.Generic.IEnumerable'1[VB$AnonymousType_2'2[pob,users]]".
Using db = New DbContext() With {.InlineParameters = True}
Dim query1 = From p In db.pob
Join u In db.users On p.id_name Equals u.id
Where p.date >= New Date(2017, 1, 1)
Group New With {p, u} By pu = New With {Key u.id, Key u.name} Into pg = Group
Select New RecentUser With
{
.id = pu.id,
.name = pu.name,
.LastDateOfUse = pg.Max(Function(f) f.p.date)
}
query1 = query1.OrderByDescending(Function(f) f.LastDateOfUse).Take(5)
Return query1.ToList
End Using
If I remove .LastDateOfUse = pg.Max(Function(f) f.p.Date) like below it works. By 'works' I mean there is no exception but of course result of query is wrong however grouping is done properly.
Using db = New DbContext() With {.InlineParameters = True}
Dim query1 = From p In db.pob
Join u In db.users On p.id_name Equals u.id
Where p.date >= New Date(2017, 1, 1)
Group New With {p, u} By pu = New With {Key u.id, Key u.name} Into pg = Group
Select New RecentUser With
{
.id = pu.id,
.name = pu.name
}
Return query1.ToList
End Using
Edit
I also tried going through navigation properties like below, but again I receive the same error.
Using db = New DbContext() With {.InlineParameters = True}
Dim query1 = From p In db.pob
Where p.date >= New Date(2017, 1, 1)
Group p By pu = New With {Key u.User.id, Key u.User.name} Into pg = Group
Select New RecentUser With
{
.id = pu.id,
.name = pu.name
.LastDateOfUse = pg.Max(Function(f) f.date)
}
query1 = query1.OrderByDescending(Function(f) f.LastDateOfUse).Take(5)
Return query1.ToList
End Using
And again if I remove .LastDateOfUse = pg.Max(Function(f) f.p.Date) like below it starts to work (proper grouping, wrong overall result).
Using db = New DbContext() With {.InlineParameters = True}
Dim query1 = From p In db.pob
Where p.date >= New Date(2017, 1, 1)
Group p By pu = New With {Key u.User.id, Key u.User.name} Into pg = Group
Select New RecentUser With
{
.id = pu.id,
.name = pu.name
}
Return query1.ToList
End Using
How can I transform above Sql query to Linq? (preferable answer in VB.Net but C# is ok too)
Solution
There is no solution yet. It looks like VB has bad Linq queries resolver - it creates unexpected method chain that can not be converted to SQL.
So instead
Group By ... Into pg = Group
we need
Group By ... Into LastDateOfUse = p.Max(Function(f) f.date).
See below full query.
Using db = New DbContext() With {.InlineParameters = True}
Dim query1 = From p In db.pob
Where p.date >= New Date(2017, 1, 1)
Group p By pu = New With {Key u.User.id, Key u.User.name} Into LastDateOfUse = p.Max(Function(f) f.date)
Select New RecentUser With
{
.id = pu.id,
.name = pu.name
.LastDateOfUse = LastDateOfUse
}
Return query1.ToList
End Using
Another problem with lambda syntax
Using lambda syntax we receive another exception.
Dim query = db.pob.
Where(Function(f) f.date >= New Date(2017, 1, 1).
GroupBy(Function(f) New With
{
Key .userid= f.user.id,
Key .username = f.user.name
}).Select(Function(f) New RecentUser With
{
.id = f.Key.userid,
.name = f.Key.username,
.LastDateOfUse = f.Max(Function(g) g.date)
}).ToList
Exception
VB.NET compiler adds unnecessary Convert to IEnumerable when generating Expression Tree.
An unhandled exception of type LinqToDB.Linq.LinqException occurred in linq2db.dll
Convert(f).Select(g => g.Date).Max() cannot be converted to SQL
GitHub
I posted an issue here.
Svyatoslav Danyliv based on my issue opened his own here.
I am getting an InvalidOperation on mscorlib.dll error on the following query and cannot for the life of me figure out why.
Here is the Class I'm populating the List(Of ) with;
Public Class ProjectionPerformance
Public SymbolId As Long
Public Name As String
Public ProjectionDate As String
Public ActualRange As Double
Public ProjectedRange As Double
End Class
Those types match the types in the table except for the date which I convert to a string
Here is the function with the LINQ query
Public Shared Function GetRangeProjectionPerformance(Optional daysToRetrieve As Integer = 100) As Dictionary(Of Long, List(Of ProjectionPerformance))
Dim todaysDate As Date = DateTime.Now.Date
Dim lookbackDate As Date = todaysDate.AddDays(daysToRetrieve * -1)
Using ctx As New ProjectionsEntities
Dim query = (From d In ctx.projections
Where d.SymbolId <= 42 AndAlso d.Date >= lookbackDate
Join t In ctx.symbols On d.SymbolId Equals t.Id
Let actualRange = d.ActualHigh - d.ActualLow
Let projectedRange = d.HighProjection - d.LowProjection
Select New With {
d.Date,
d.SymbolId,
t.Name,
projectedRange,
actualRange}).GroupBy(Function(o) o.SymbolId).ToDictionary(Function(p) p.Key,
Function(x) x.Select(Function(y) New ProjectionPerformance() With {
.SymbolId = y.SymbolId,
.ProjectionDate = y.Date.ToString(),
.Name = y.Name,
.ActualRange = y.actualRange,
.ProjectedRange = y.projectedRange
}).ToList())
Return query
End Using
End Function
I'm getting that error on this part of the LINQ query (Im assuming that is that portion is highlighted in green in VS2013)
Function(x) x.Select(Function(y) New ProjectionPerformance() With {
Do I have to retrieve the actual field values and eliminate the Let statements and do the calcs in the List function of the Dictionary call?
Based on your comments, I suspect that the problem is that you try to assign null values to the double properties in ProjectionPerformance. It should work if you change your code as follows:
Dim query = (From d In ctx.projections
Where d.SymbolId <= 42 AndAlso d.Date >= lookbackDate
Join t In ctx.symbols On d.SymbolId Equals t.Id
Let actualRange = d.ActualHigh - d.ActualLow
Let projectedRange = d.HighProjection - d.LowProjection
Select New With {
d.Date,
d.SymbolId,
t.Name,
projectedRange,
actualRange}).GroupBy(Function(o) o.SymbolId).ToDictionary(Function(p) p.Key,
Function(x) x.Select(Function(y) New ProjectionPerformance() With {
.SymbolId = y.SymbolId,
.ProjectionDate = y.Date.ToString(),
.Name = y.Name,
.ActualRange = If(y.actualRange, 0.0),
.ProjectedRange = y.projectedRange
}).ToList())
In order to spot such errors before running the program, you should set OPTION STRICT to ON (either on project or file level).
How do I perform group in LINQ inside vb code (dot.net v4.0) with DataTable and sum on the group?
In the sample below I need to add group by GroupName, ProductName and perform sum on QTY. The columns, order and where should remain as in sample, I just need to add the group and sum. The format should remain the same (getting row using e("FieldName")).
Dim ordersTable As DataTable = _dsProd.Tables("tblProductSummary")
Dim query =
(From e In ordersTable
Where (e("Type").ToString() = "1" Or IsDBNull(e("Type")))
Order By e("GroupSortOrder") Ascending, e("ProductName")
Select
GroupName = e("GroupName"),
ProductName = e("ProductName"),
QTY = e("QTY"),
Type= e("Type")
)
Dim query =
(From e In ordersTable
Where (e("Type").ToString() = "1" Or IsDBNull(e("Type")))
Order By e("GroupSortOrder") Ascending, e("ProductName")
Group e By Key = New With {
.ProductName = e("ProductName"),
.GroupName = e("GroupName")
} Into Group
Select New With {
.ProductName = Key.ProductName,
.GroupName = Key.GroupName,
.Sum = Group.Sum(Function(x) x("QTY"))
})