VS 2008 Linq Possible To Use Query In Another Query?
Apr 16, 2011
I was wandering is it possible to use a query within another query below is the code I am trying to use.
Public Function GetInventByComp(ByVal CompID As String) Using DC As New DataClassDataContext
'need to get company id's based off names? thats bad should be name from Id need to rethink this
Dim invent = (From C In DC.Inventors_Companies _
Where C.CompID = CompID _
Select C.InventorID).ToString
[Code]...
I was trying to us multiple values in a string like "1, 3, 5" but I can't seem to get that working either so I am trying to use just a single value now. Can anyone help me? "Yes I am new to this"
I know that LINQ queries are deferred and only executed when the query is enumerated, but I'm having trouble figuring out exactly when that happens.Certainly in a For Each loop, the query would be enumerated.What's the rule of thumb to follow? I don't want to accidentally enumerate over my query twice if it's a huge result.
For example, does System.Linq.Enumerable.First enumerate over the whole query? I ask for performance reasons. I want to pass a LINQ result set to an ASP.NET MVC view, and I also want to pass the First element separately. Enumerating over the results twice would be painful.It would be great to turn on some kind of flag that alerts me each time a LINQ query is enumerated. That way I could catch scenarios when I accidentally enumerate twice.
I have to join two main tables, and I need to filter the results by elements in an ASP.NET web form. These filters are created on the fly so I have to use a lot of where extensions to filter the query. I want to execute the query with as optimized SQL as possible.
I am first doing a simple join between TW_Sites and TW_Investigators. Then there are two sub-tables that are involved. TW_InvestigatorToArea and TW_InvestigatorToDisease. While most of the where clauses are working fine, I have found a performance issue that won't be an issue right now, but will be an issue as the table gets bigger.
The arrays DiseaseCategories and DiseaseAreas would be the results of a CheckBoxList result.
Protected Sub LoadResults() 'Get Dictionary of Filters Dim FilterDictionary As OrderedDictionary = Session.Item("InvestigatorFilterDictionary") ' Initialize LinqToSql
I encountered something like a logical error which I could hardly resolve since I'm new to this technology. I'm using visual basic 2008 express edition with its built-in linq-to-sql technology. I was able to retrieve, add, edit, and delete such record using the linq-to-sql method, but one thing.I could not get is something like relational database operation. Here is my problem. As you can see the table above which represents the records on my database. You can notice there some account numbers that were duplicated which I used as the primary key or identifier. What I want is when I'd like to query such account number it should display all the records that have the same account numbers on it. Say for example, if I query the account number 00003. It should only pull up and display three records with the name Maverick and their corresponding address, movie rented and date.What is happening in my end is when I query such account number which are being duplicated in the database I encountered two things, its either it would display all the records in the database with different account numbers associated or it gives me an error message if I change my code from 'For Each memrec In db.Table3s' to 'For Each memrec In retrn' statement.What I've been trying to do here is if you enter the account number on the search box, it should only display the records on the combo box associated with the account number being entered. Like if you enter 00003 on the search box, it should only display the three movies rented by Maverick no more no less on the combo box. [code]
I have already tried that set of codes before but it's working the same thing. I tried many times modifying my codes before I posted my comment in this forum thinking that i can resolve it on my own but I wasn't able to. That code won't still filter the records in the database. I would like to verify that the table above is only representation but the real column on the table on my database is 'Account#' not Account Number and visual basic would detect the code as 'Account_'. May i know why Movies_Rented column on my table is not a member of string? Why is it the code you gave would still display all the records on the combo box? this is what im not getting. hope you can still find the solution to this issue.
Is there a way to convert a string into a linq query? Searching for those words brings up tons of stuff unrelated to what I'm trying to do..For instance, this works, of course...
Dim lstMyQuery = (From item in htMyTable.values where item(0) = "Apple" Select item)
But somehow I want to do this:
Dim strQuery = "From item in htMyTable.values where item(0) = " & CHR(34) & "Apples" & CHR(34) & " Select item" Dim lstMyQuery = (Somehow run/convert strQuery as a query)
The reason is strQuery will be different each time depending on what the user has selected earlier in the program.R if lstMyQuery is already a collection, is there a way to add to it?
Dim lstMyQuery = (From item in htMyTable.values where item(0) = "Apples" Select item)
(this obviously doesn't work, but it's basically what I want to do...)
lstMyQuery.Add(From item in htMyTable.values where item(0) = "Oranges" Select item)
i need to query the datatable & set the outcome as datagridview controls datasource
vb.net Private Sub Txt_Search_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Txt_Search.TextChanged 'routine objective:- Filter datatable & set the datagridview datasource
If I use a LINQ query over some type of collection, is there any way to know the initial index of an element of the result?
Purpose: I make a query to set as source of a DataGridView, and on a (button)cellclick event I want to a call a method that needs to reference the collection at the correct index.
I have a LINQ query that groups and counts on a single dgv cell. What I want to do is group and count on 2 dgv cells. So I modified my existing query by adding a SELECT statement highlighted :
CODE:
But I am getting an error on the second select variable stating: Range variable 'Value' is already declared
What I have read shows that I can select more than one variable.
I'm trying to do a LINQ Query against a typed datatable that will return me duplicated data.With out going into too much detail, here's the basic setup:
strCode1 - string type intCode1 - int32 type intAdjustor - int32
There are more fields but these are the ones that are important.I'm going to do my best to describe this, as it's kind of confusing.In theory intCode1 is a key for strCode1 (hence the names). So each time intCode1 is duplicated, the same strCode1 should appear. Example:
[code]...
Ultimately I'd like to get a List(Of T) - where T is my typed data row. In SQL, I would simply use a sub query, to get a distinct list of strCode1 and intCode1, then do a count, grouped by strCode1 where I get more than one row.I'm not sure how to translate that into LINQ, AND get the original types data rows returned in a list.
I'm using a DataGridView to post the results of LINQ-from-SQL query. I was hoping that the data would be editable in the DataGridView, but it isn't. I made sure that DataGridView.readonly = false. I'm using VB.
VB 2008 DB = New CXToolDataContext() Dim Systems = (From TBLSYSTEMS In DB.tblSystems, TBLSYSTYPES In DB.tblSystemTypes _ Where TBLSYSTEMS.ProjectName = projectnumber And TBLSYSTEMS.SystemType =
When Creating a query using the sear Criteria Builder . I keep getting the error : "The schema returned by the new query differs from the base query" what does that mean and how do i avoid this problem in future
Forgive my ignorance on this.I have this LINQ Query:Dim ngBikersDataContext As New CarBikeWalkDataContext
bikersList = (From c In ngBikersDataContext.Reg_Bikers _ Order By c.L_Name _ Select New Bikers() With { _ .BikerID = c.BikerID, _ .F_Name = c.F_Name, _
[Code]...
with the error "Overload resolution failed because no accesible 'Select' accepts this number of arguments." Over the "NEW" I get an error " ')'expected."
I've been reading a fair bit about the performance of using LINQ rather than using a for each loop and from what I understand using a LINQ query would be a little bit slower but generally worth it for convenience and expressiveness. However I am a bit confused about how much slower it is if you were to use the results of the query in a for loop.
Let's say that I have a set called 'Locations' and a set of objects called 'Items'. Each 'item' can only belong to one 'location'. I want to link items that are under the same location to each other. If I were to do this using a normal 'For Each' loop it would be something like this:
For Each it as Item in Items If it.Location.equals(Me.Location) Me.LinkedItems.Add(it) End If Next
However if i was to use LINQ it would instead be this:
For Each it as Item in Items.Where(Function(i) i.Location.equals(Me.Location)) Me.LinkedItems.Add(it) Next
is the second (LINQ) option going to loop once through the entire 'Items' set to complete the query, then loop through the results to add them to the list, resulting in essentially two loops, or will it do the one loop like the first (For Each) option?
Is it possible to do the following? [code] Basically I have one Load_Gridview function that is called on all postbacks, and rather than creating a bunch of different cases.I want the filters to stack.My actual code has more filters set up (4 or 5 of the).It all compiles ok but when I run and try to execute with active checked, or a department selected I get the following error. [code]
We are doing a query against an in-memory collection of LINQ data objects. The wrinkle is that we are ordering by a column in a related table whose records have not necessarily been loaded yet (deferred loading:)
Dim oPkgProducts = _ From b In oBillPkg.BillProducts _ Where b.Successful.GetValueOrDefault(Common.X_INDETERMINATE) = _
How do I add ROW_NUMBER to a LINQ query or Entity? How can I convert this solution to VB.NET?
[Code]...
I'm having trouble porting that last line. I have been unable to locate a VB.NET example. I'm actually not looking for any paging functionality like the example provides, just good old-fashioned Row_Number(Order By X) row index.
I have been trying the following but it returns unexpected results:
Dim xd As XDocument = _ <?xml version="1.0" encoding="utf-8"?> <root>
[code].....
The above result returns both 'element' nodes however it should only return the first where element/subelement@id=1/subsubelement@id=3 However if results.Ancestors. is used it returns the correct 'subelement' and if that line is not included it returns a single 'subsubelement' whih is also correct I don't understand why when mvoing to the 'element' it returns both (I realise both have a subelement with id=1 but I thought each further query would filter out the presvious results)?
I have a List of Price Objects (Price contains Date, High, Low) and am trying to extract monthly averages via LINQ. I have this working in C# but we have a few legacy applications that need it in VB.Net and I can't quite seem to figure out the conversion. I've even tried breaking it into two queries to no avail.
Ok im trying to do a if statement in Linq and was wondering if it was possible to do something like:
Dim loadFriends = From p In db.UserRelationships Where p.aspnet_User.UserName = User.Identity.Name _ Or p.aspnet_User1.UserName = User.Identity.Name And p.Type = 1 _ Select New With {if p.aspnet_user1.user = "a certan username" then .username = _ p.aspnet_user.username else .username = p.aspnet_user1.Username}
Dim query = From o In myContainer.MyObjects Select o.MyStringProperty Distinct Dim myProperties As List(Of String) = query.ToList????? 'no way!!!' "query" type is IEnumerable(Of String)
I tried to use the query directly as a DataSource of a (infragistic) combobox, but it throws me NullReferenceException, so I decided to convert it to a listof strings, to be a more "classical" datasource.
Dim values As List(Of String) = query.AsQueryable().ToList() does not work either: Value of type 'System.Collections.Generic.List(Of System.Linq.IQueryable(Of String))' cannot be converted to 'System.Collections.Generic.List(Of String)'.
