.net - How To PLINQ An Existing LINQ Query With Joins
Sep 28, 2011
I'm using LINQ to compare two DataSets with each other to create new rows and update existing. I've noticed that the complete comparison lasts ~1,5 hours and only one of the two cores is busy(Task-Manager is 50-52% CPU Usage). I assume that it could increase performance significantly.
how and what should I parallelize?
These are the original queries(reduced to the essentials):
'check for new data
Dim srcUnique = From row In src.Email_Total
Select Ticket_ID = row.ticket_id, Interaction = row.interaction, ModifiedAt = row.modified_time
[Code].....
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Oct 18, 2011
I'm trying to figure out how to use Group Joins in LINQ queries under VB.net. For some reason, every example I seem to find on the syntax is just plain At least, that's what my compiler keeps telling me. This is a simple example where I want to join orders to their order items so that I end up with a type that contains a collection of order items grouped together by their orderId's:
Dim groupedOrders = (From o In orders
Group Join i In orderItems On o.OrderId Equals a.OrderId Into myOrders
Select o.OrderId, myOrders).ToList()
What I'm currently running into in this example is that the 'myOrders' group I'm creating errors out with: Definition of method 'myOrders' is not accessible in this context.
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Mar 7, 2011
Can anyone help me by translating this SQL Statement to Linq? [code]
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Sep 22, 2009
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.
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Jul 14, 2011
given this function:
Public Function Search(ByVal StartIndex As Integer, _
ByVal MaxResults As Integer, _
ByVal AccountNumber As String, _
ByVal LastName As String, _
[Code]....
instead of what I expected:
Select count(*) from remitline where lastname = "smith"
What am I doing wrong building up the where clause? I'm using Castle ActiveRecord 2.1
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Aug 6, 2009
if there is that much of a performance gain in running a LINQ stored procedure versus a LINQ query?
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Nov 19, 2010
Is it possible to use PLINQ on visual studio 2008 framework 3.5
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Sep 14, 2010
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
[code]....
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Mar 31, 2011
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."
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Aug 17, 2009
I'm having trouble adding child elements to the below
<securities>
<security id="040104JC6">
[code]....
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Apr 5, 2011
I'm using VB.Net to create a windows form application. One form has a DataGridView that displays data from a SQLServer table via a TableAdapter and BindingSource whose filter is set as I need it. Elsewhere on the same form I would like to show totals for four columns of the same table, but from a totally different set of rows. All I've been able to figure out is to create another TableAdapter - but this seems foolish since the SQL table data has already been brought into my application by the first TableAdapter.Is there a way to run a query on the DataTable that was filled by the first TableAdapter, and how do I get the query results?
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Jun 17, 2010
I'm trying to create a LINQ query (or queries) that count the total number of occurences of a combinations of items in one list that exist in a different list. For example, take the following lists:
CartItems DiscountItems
========= =============
AAA AAA
[code]....
The result of the query operation should be 2 since I can find two combinations of AAA and BBB (from DiscountItems) within the contents of CartItems.My thinking in approaching the query is to join the lists together to shorten CartItems to only include items from DiscountItems. The solution would be to find the CartItem in the resulting query that occurs the least amount of times, thus indicating how many combinations of items exist in CartItems.When CartItems is filtered to only the items in DiscountItems, it can be visually displayed like this:
CartItems that get a discount
=============================
AAA BBB <= This combination is eligible for a discount
AAA BBB <= This combination is eligible for a discount
AAA <= Not eligible
Thus, because there are 2 combinations of the discount in the Cart, the result is 2.Here's the query I already have, but it's not working. query results in an enumeration with 100 items, far more than I expected.
Dim query = From cartItem In Cart.CartItems
Group Join discountItem
In DiscountGroup.DiscountItems
[code]....
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Jan 27, 2011
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) = _
[code]....
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Aug 31, 2011
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.
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Mar 17, 2009
Has anyone a sample code, or point me towards a guide on how to link in a Query from an existing Access Databse into my vb? Im wanting to populate some text boxes with information from a query.
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Aug 31, 2011
I don't know if this is doable, maybe with Linq, but I have a List(Of MyType):
Public Class MyType
Property key As Char
Property description As String
End Class
And I want to create a Dictionary(Of Char, MyType) using the key field as the dictionary keys and the values in the List as the dictionary values, with something like:
New Dictionary(Of Char, MyType)(??)
Even if this is doable, internally it will loop through all the List items, I guess?
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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"
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Jun 27, 2011
I have a text file that needs to be uploaded to a ftp , however it needs to overwrite any existing file with that name.the filename will never change but data inside does, thats why we need to upload it to provide the most current data.filename = rawdata.txt..I have a basic form with a timer or button to send the file, I just need the code. In the mean time im messing with my last post code to see if there is a way to modify it to upload files but not having much luck.You Know Your Addicted To Computers When - Your main computer is a 7 terabyte, Core2Quad 3 Ghz +, with 4 or more gigs ram, over 200 programs installed, and you would rather sit with it programming than go to the movies!I've got 13 PC's in the House and 7 are in my bedroom and my main one exceeds this set of stats. Does anyone know a good psychologist?
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Jan 25, 2012
Dim dbCMD As New OleDb.OleDbCommand With {.Connection = dbConn, .CommandText = _
<SQL>
SELECT *
FROM (tblServices
7INNER JOIN tblAgents AS Agent1 ON tblServices.SentByID = Agent1.AgentID)
[code]....
I understand the error, Agent1 doesn't exist for the name.
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Feb 21, 2012
I am trying to do multiple joins within a single query in SQL Server CE. I know that SQL Server CE doesn't support multiple SELECTs but I can't find any information on multiple INNER JOINs. I keep getting token errors on ProjectItemMaster (after the FROM) and the first INNER JOIN. Warning this is a big ugly query used to generate reports.
[Code]...
If I can't uses multiple INNER JOINs I can I break the query down into a number of different queries but I would prefer not to. So it is easier to maintain a SQL Server CE and an SQL Server version of the program.
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Jan 19, 2010
We use an ERP program in conjuction with SQL server and lots of tables that keep track of product records customers and all these kinds of stuff. I am building a fairly simple Warehouse Inventory Application that warehouse employees will use to count and inventory stock on hand from products around the warehouse and then check if any quantity errors occur between stock on hand and logistic quantities.I have created a custom Inventory table that I would populate with records like {stock_code, Description, Quantity_remain, quantity_avail}. Those records already exist in 2 different tables in my database. The aim is that I want my program to fetch daily 10 random codes from the stck table, and records about their quantities,bringing together the "columns" that my new custom table has +2 more editable columns: inventory, date, user with a query like this:[code]
As you can imagine my custom table contains the exact same fields as the query suggests + 3 more.I use the the stck table to fetch product info like its code,description, its group_code, categ_code, and then I outer join the stck_x_th that contains records concerning quantities remaining or available asociated with each product code and the "places" those quantities reside in the warehouse.Then, store them in a datagridview control, with only one editable column -inventory- (user and date columns are auto-populated with default values), and then when the user fills out the inventory quantites, I want to save the datagrid "as it is" in my new custom table.I am creating a databound gridview control using one table adapter (which refers to the inventory table). Then I add to my table adapter using "add query" the forementioned query with a fillby method to populate the Datagrid (and therefore my Table in SQL) with the exact same values my query returned from the different tables. But whenever I try to update the table concurrency exceptions raise.It works like a charm if I enter the values in the grid cells manually, without populating the grid control with the new fillby method my self but not if I populate the grid via a query and then hit update.
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Sep 4, 2009
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?
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Mar 24, 2012
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]
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May 5, 2009
I have below XML file
<?
xml version="1.0" encoding="utf-8" ?><
PageFlow>
<
attributegroup name="Search"><
attributes>
[Code]...
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Apr 18, 2012
I am looking to sum the "Status" field.
Dim _detailRecords As New DataTable
_detailRecords.Columns.Add("y")
_detailRecords.Columns.Add("z")
[Code]....
I'm also wanting to keep this as an IEnumerable of DataRow because I will be creating a datatable from it with
Dim yyyyy As DataTable = query8.CopyToDataTable
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Aug 13, 2010
I am Fairly new to Linq and I am trying to write a simple query to return the error messages within my xml file.
<?xml version="1.0" encoding="utf-8"?>
<Error xmlns="urn:xxxxx">
The following errors were detected:
[code].....
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Aug 26, 2009
if I run this under c#
from p in Addresses where p.Address2 == null select p.AddressID
it generate this query
SELECT [t0].[AddressID]
FROM [dbo].[Address] AS [t0]
WHERE [t0].[Address2] IS NULL
if I run this under vb.net
from p in Addresses where p.Address2 = nothing select p.AddressID
it generate this query
SELECT [t0].[AddressID]
FROM [dbo].[Address] AS [t0]
WHERE [t0].[Address2] = ''
p.Address2 is a varchar field that accept null value
why vb.net is "wrong" ?
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Dec 1, 2009
I'm converting the Linq query below from C# to VB.Net. Can you spot my error? The query joins 3 XML datasets. C# - This one works great.
List<Course> courses =
(from course in CourseXML.Descendants(ns + "row")
join coursecategory in CourseCategoryXML.Descendants("Table") on (string)course.Attribute("code") equals (string)coursecategory.Element("DATA")
[code]....
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Mar 14, 2011
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)?
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Feb 22, 2012
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.
[Code]...
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