Using Linq For Object Dataset Processing?
May 26, 2011
I have a collection (IList(Of Sample)) of the following class:
Public Class Sample
Public sampleNum As String
Public volume As Integer[code].....
This collection is filled from a regex that gets passed over a file.What I want to do is use Linq to generate a collection of these for each unique samplenum using the following conditions.For each samplenum: Have the highest volume where the final is greater then one
If the sample has multiple records for this volume then pick the one with the the highest final
If the previous step leaves us with no records pick the record with the highest final ignoring volume
I am extremely new to Linq and just can't get my head around this. For now I have solved this using for each's and temporary lists but I am interested in how this would be handled using pure Linq.Sample Data:
samplenum | volume | initial | final
1 | 50 | 8.47 | 6.87
1 | 300 | 8.93 | 3.15[code]......
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Mar 18, 2011
I just learned some basics of multi threading in VB.net recently as I came across processing a large List of records and inserting them into SQL database one by one.
I have code look like this:
Private Sub btnLoadNow_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLoadNow.Click
Dim autoLoad1 As New Thread(AddressOf AutoLoad)
autoLoad1.Start()
[CODE]...
Itemlists is a global lists i retrieved from database, everything looks fine to me but when i run this program, I found that the threads are inserting one records 9 times into the database(I have 9 threads in total), which makes me think that maybe i need to specifically assign 1/9 of a list to each thread? Is there another way to do it which doesn't require the splitting of the list, if not , how do i split it then assign?
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Jan 6, 2010
2008 Array Processing and Sequential File Processing
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May 19, 2011
Im a college student and this is my first programming class, i am having extremely diffcult time with arrays and sequential file processing. Im not asking for the whole program, just something to get me started and hints along as i progress with it. Please help me get started on my program, its due in 2 days.
Here are the requirements....
1. The program must input any number of individual�s last and first names using two separate textboxes.
2. The array of names must be sorted by the last name using a bubble sort. You must code the sort.
3. The program must be able to recall the names from the file and add to the existing list of names so that more names can be added to, sorted, and written back to the file in sorted order.
4. Sort in ascending order: A to Z
5. All names must be displayed in a listbox in sorted order when the user wishes to see them.
6. In the listbox the last and first names must be separated by a comma and a space. Example: Smith, Mary
7. The user must be able to search for a name in the array, using the binary search algorithm. You must code the search.
8. Do not use module-level variables. Instead you may choose to use Static.
9. The program must be designed using Visual Basic 2008
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Jul 29, 2011
I am getting following error whenever I want to use IIf function inside entity framework query.
LINQ to Entities does not recognize the method 'System.Object IIf(Boolean, System.Object, System.Object)' method, and this method cannot be translated into a store expression.
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Oct 21, 2009
How can I convert an object of type System.Data.Linq.DataQuery to System.Linq.IQueryable?I'm working with Visual Basic/Silverlight, and the source code of my query is as follows:
Public Function Get_Cli_Pag() As IQueryable(Of V_Cliente_Pagare)
Dim Qry = From P In Me.Context.Pagares Join C In Me.Context.Codigos On C.Codigo
[code]....
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May 18, 2010
I have a dataset that is populated via a SQL Stored Procedure, the format of which is below: Country | Brand | Variant | 2004 | 2005 | 2006 | 2007 | 2008 The number of rows varies between 50 and several thousand. What I'm trying to do is use Linq to interrogate the dataset (there will be several Linq queries based on user options), but a simple example would be to SUM the year columns based on Brand. I have the following that I believe creates a template for me to work with: But from here on I'm absolutely stuck!
[Code]...
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Jul 14, 2011
Background: I'm importing data from a MySQL database into a SQL-Server database(for reports and later a SSAS-Cube). I want to normalize the data at the same time. I want to group repeating Ticket_IDs to one record in a table Contact with other useful informations and leave the rawdata in the sub-table ContactDetail(with foreignkey to Contact).Hence every record in Contact has a unique Ticket_ID.
I've decided to use strong typed datasets for the import. Now i'm wondering what's the best way to detect if i've already added a Ticket_ID. I could check for it in every loop(~100000 records) but i'm assuming that there is a better/faster way.
Simplified sample-data:
Ticket_ID ID fiContact
89442226 1 1
89442226 2 1[code].....
I will have a look if this is faster than the iterating approach with a HashSet to detect if the contact was already created.
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May 20, 2010
I've got the following LINQ Statement:[code]invRecord.Pack_Num is a field of type Integer. This means that when I try to access it, if it is DBNull I get a StronglyTypedException. The above code throws this exception. If, however, I remove the "invRecord.Pack_Num = PSNum" and in its place put something like "True", the code works fine. So I guess my question is, why is that that invRecord.IsPack_NumNull() returns False when the value is in fact DBNull and what can I use as a conditional instead? I've been beating my head against the wall for a while now and I can't find a solution to this problem.
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Apr 4, 2009
linq querying various nested tables in a dataset? I can't find something like that on the net.
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Jun 4, 2012
I am using VS 2008, VB.NET and Windows XP r3.I am trying to use LINQ to DataSet in my app. In my test app, I can get it to work find. My test form has an OleDbDataAdapter, an OleDbConnection and a DataSet. It also has a DataGridView bound to the one table in the DataSet, a BindingSource and a Button.[code]
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Nov 12, 2011
I've got the following LINQ Statement:
[code]...
invRecord.Pack_Num is a field of type Integer. This means that when I try to access it, if it is DBNull I get a StronglyTypedException. The above code throws this exception. If, however, I remove the "invRecord.Pack_Num = PSNum" and in its place put something like "True", the code works fine. So I guess my question is, why is that that invRecord.IsPack_NumNull() returns False when the value is in fact DBNull and what can I use as a conditional instead? I've been beating my head against the wall for a while now and I can't find a solution to this problem.
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Aug 20, 2010
I have a single columned datatable inside a single tabled dataset.I just want to convert this dataset to distinct rows. Here is my code, it gives compile error '.' expected.
Dim query = _
From email In ds.Tables(0) _
Select email.Field<string>("Email").Distinct()
EDIT: I changed to (Of String) and it works... BUT NOW 'query' is an ienumerable collection of characters... not a datatable... so how do I convert back easily without manually doing a loop?
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Jun 14, 2012
i think i have not represented my question correctly here My LEFT OUTER JOIN MSDN reference is here to visualize my problem in access databaseTABLE "T1"1234567TABLE "T2"1,sunday2,monday i need output as 1,sunday2,monday34567 i need it to done through LINQso far i did is here
Dim RIGHT_table As DataTable = ds1.Tables("t1")
Dim LEFT_table As DataTable = ds2.Tables("T2")
Dim OutPut = From LEFTsource In LEFT_table.AsEnumerable(), RIGHTsource In RIGHT_table.AsEnumerable() _
[code]...
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Jan 29, 2008
This is what I'm doing to select and display 3 columns of my datatable in GridView:
Dim myCustomers = From Cust In myDataset.Customers _
Select CustomerId = Cust.CustomerId, _
CustomerName = Cust.CustomerName, _
ExpiryDate = Cust.ExpiryDate
DataGridView1.DataSource = myCustomers.ToList
The expiry date has null values in many records whose expiry date is not set.On executing the query I get runtime error:System.Data.StrongTypingException "The value for column 'ExpiryDate' in table 'Customers' is DBNull."
Obviously, my LINQ query is wrong or incomplete, but I am not able to figure the way to do it correctly.
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Feb 7, 2012
I have following code that creates Linq query.
I've never used Linq until today and having problem with "Order By Clause"[code..]
If I run the code, I get following error.Name 'p' is either not declared or not in the current scope. How come p!Weight in "Select Clause" works but not in "Order By Clause"?
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Apr 19, 2010
I have used a datarepeater with a dataset and it was simple to implement by dragging fields from the Data Sources window onto the DataRepeater control
I am trying to use Linq as a data source instead of dataset.
How do I bind data to textbox with Linq for Datarepeater?
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Mar 17, 2009
Right now our queries can be driven through the DataTable Select statement. However, utimately we want to end up with more complex queries. We think Linq is the answer, but can't find anyexamples of this.Here is the sysnopsis:I have a dataset containingdatatable(s) of informationI have a datatable containing business rules as strings like:
(ISNULL(MEMLNAME, '') = '')
(#1880/01/01# <= CONVERT(BIRTHDATE, 'System.DateTime') AND CONVERT(BIRTHDATE, 'System.DateTime') <= #2009/12/31#)
[code].....
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Aug 26, 2011
I have a DataSet where I need to filter the collection where one of the date columns is not null.
How do you term this in LINQ?
This is what I have so far but there is a compiler error on the w.CompletedDate field in the Where clause.
Dim completed = From ins In InspectionDataset.Inspection.AsEnumerable _
Where (Function(w) w.CompletedDate IsNot Nothing) _
Order By ins.Field(Of DateTime)("UpdatedDate")
I have also tried it the below way but the compiler will not allow the DBNull comparison.
Dim completed = From ins In Inspection.AsEnumerable _
Where ins.Field(Of DateTime)("CompletedDate") <> DBNull.Value _
Order By ins.Field(Of DateTime)("UpdatedDate")
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Feb 8, 2012
I have been searching for quite a while about joining multiple datatables via LINQ to dataset (When i say multiple, i don't mean just 2!!!), and it seems there aren't lot of examples in the net. I have seen examples of joining two datatables, done that, no problem there. Now i want to join three datatables. And there's nothing i can find out there.For example i have a 3 datatables:
PERSON (columns: person_id, name, gender_code, ethnic_code)
GENDER (columns: gender_code, gender_description)
ETHNICITY (cols: ethnic_code, ethnic_description)
[code].....
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Mar 2, 2012
I am trying to convert my EnumerableRowCollection into a DataTable, but I can't see the CopyToDataTable method. The enm.CopyToDataTable() has the blue saw tooth line under it with error saying " 'CopyToDataTable' is not a member of 'System.Data.EnumerableRowCollection' ". I have set a Reference to System.Data, System.Data.Linq, and System.Data.DataSetExtensions. I thought the CopyToDataTable method was part of the System.Data.DataSetExtensions, right? Anyone know why I can't access this method?
[Code]...
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Apr 30, 2009
from a performance point of view is it faster to work with linq to sql or dataset.datatable?
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Jan 13, 2011
How can I use dynamic fields in LINQ in the PART OF THE where query? I mean that I want to write where x = *dynamic fields* I want to do the select query in all of the tables that are in the dataset, not on one datatable.
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Jun 13, 2012
i am having 2 tables one table stores the WEEK-days another table stores the WEEK-days + other fields.i need the LINQ query to return all WEEK-days + other fields just like SQL LEFT JOIN query so far i did is [code]....
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Feb 10, 2011
The query works but only retrieve the joined rows, i want to retrieve all rows in the first datatable.My current query:
vb.net
Dim q = From regE In (From registoE In _dtRegistosAEnviar.AsEnumerable
Group registoE By colaborador = registoE.Field(Of String)("Colaborador") Into grupoE = Group
Select New With {
[code]....
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Mar 15, 2010
Ive have a listview on my form and need to populate it with data from my Table called "tblCustomers". However I need to only retrieve records based on field that is populated with data called "Joe". In order for the SQL syntax to retrieve the name "Joe" then the SQL syntax needs to reference the Label on the form called "lblName" which will have the name "Joe" as the caption.
How can my dataset have SQL data that references my label object on my form?
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Jan 27, 2012
I have the following line of Dim clients = From client In db.clients Select client Where client.ClientID = id
In debugging, the clients object populates perfectly, but how can get get data from the clients object? Like if the clients object has a FirstName property, how can I set a textboxes text property to that property from the clients object?
I thought it'd be something like:
tbClientFirstName.Text = clients.FirstName But that doesn't work.
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Mar 1, 2010
how to convert a linq query directly back to the same object type. But I have failed!
Dim test(2) As myStructures.ReturnData
test(0).Partnumber = "2055"
Dim result = From n In test _
Where n.Partnumber = "2055"
'now convert result to a myStrucutres.ReturnData() how?
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Apr 3, 2012
I was given a task of rewriting some Crystal Reports. I found the original reports circa 1999, opened them up in VS 2008 made the changes and saved them.Now, they reference a database that is no longer around. So, I deleted this data source and added a .NET OBJECT datasource. I changed everything around so that the fields now look at this new datasource.
My intent was to create the report and during run time, pass it a datatable. This table is created by running a sproc created.When I run it, I get the first page of the report. But when I try to change pages or print, I get an error: Logon failed. Details: crdb_adoplus : Object reference not set to an instance of an object. Error in File C:...MR01 {8E5164A9-4B01-4019-81E6-87AED65A02DF}.rpt: Unable to connect: incorrect log on parameters
[Code]...
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Apr 1, 2009
I have an XML File that I am processing using LINQ. I want to basically serialize the XML data into custom objects but don't know how.
[Code]...
How can I finish the above LINQ query to populate the Children property of the Group object?
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