.net - How To Work With Dataset's Datarelation In Linq
Apr 4, 2009linq querying various nested tables in a dataset? I can't find something like that on the net.
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Datarelation Within A Dataset?
Apr 11, 2010My question is : If I have two or more fields in table1 pointing to the ID field of Table2...would I be able to set the datarelation between the two tables by setting the 1st relation between table1 to table2 against the relevant ID fields from both the tables and then go on to create and add new datarelation between the same tables again...but this time against the 2nd field from the table1 to the ID field of table2. Or would I need to load table2 that many number of times into the dataset as there are fields pointing to it from the table1?
View 7 RepliesDataSet, DataRelation And DataBinding?
Oct 19, 2010I have two combobox, cmbCountry and cmbLocationI have dataset with 3 table, first table for Country value, second table with Location value and then I have table Apartments with IDCountry and IDLocation.I have 2 datarelation, ApartmentCountry, ApartmentLocationThen I bind the last table with cmbCountry and cmbLocation
View 2 RepliesLINQ Group By Multiple Values Does Not Work Well But Work Well In C#
May 29, 2012I found that when group by multiple values does not work well with VB.NET, but it works well with C# ,here are my code, is there something wrong with my VB.NET Code? Here is my VB.NET code:
[Code]...
.net - DataRelation From A Single Query?
Apr 4, 2009i have the following piece of VB.NET code:
Dim conn As New MySql.Data.MySqlClient.MySqlConnection(ConnectionString)
conn.Open()
Dim sql = "SELECT * FROM users"
Dim com = New MySql.Data.MySqlClient.MySqlCommand(sql, conn)
Dim ds As New DataSet("dsUsers")
[Code]...
Datarelation Between A Datagridview And Listboxes?
Dec 17, 2008I have a datagridview (parent) and a (well, several) listboxes that I am trying to create a relation with.Datagrid has master records which contain ID fields to lookup tables. The lookup tables are populated into listboxes.I have 1 dataset which contains tables for my datagridview(s) and my listboxes.I need to create the relations so that when they click on a row in the grid, it shows the corrisponding item in the listboxes as well.Problem is, a lot of the ID's in the parent table are empty... so when I try to create the relation, it blows up.
Code: "This constraint cannot be enabled as not all values have corresponding parent values." I'm doing like like so
Code:
lo_relation = New DataRelation("RelationName",DataGridTableIDColumn, ListboxTableIDColumn)
I tried to reverse it, naming the ListboxTableColumn as the parent. That allows the relation to build, but I can't set the Listboxes .ValueMember to that...I'm kind of stumped... as it needs to be a two way relationship.
1) When the parent record (datagridview) changes, it changes the value in the listbox
2) When the Listbox changes, it changes the "value" in the parent datatable so it can be updated.
Would I resolve my issue if I populated the parent with a "default" ID in each field (say 0)... if the database value is null? And furthermore, populate each lookup table with a "blank" default value as well? i.e. First record is ID = 0, Desc = ''?
Asp.net - Using Linq On A Dataset
May 18, 2010I 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]...
XML In A Dataset Without Significant Work?
Feb 15, 2010Question:Using VB.NET/C#, is it really not possible to read the below XML in a dataset without significant work ? I tried
oDataSet.ReadXml(strFileName)<BR>and
Dim oDataSet As System.Data.DataSet = New System.Data.DataSet
Dim strLocation As String = Environment.GetFolderPath(Environment.SpecialFolder.Desktop)
strLocation += System.IO.Path.DirectorySeparatorChar + "filename.xml"
oDataSet.ReadXml(strLocation)
But all this is doing is putting ONE row with one cell with content "2010-02-12T10:33:39" in my dataset.
[Code]...
.net - Can't Get Linq To NHibernate To Work?
Nov 22, 2009I'm struggling with getting Linq To NHibernate to work.I have referenced NHibernate, NHibernate.Linq and NHibernate.ByteCode.Castle . Also I have all other dependencies in the same folder.
Code / Error message:
Public Function GetProjectsByName(ByVal ProjectName As String) As List(Of Project)
Return (From x In _session.Linq(Of Project)() Where x.Name.Equals(Project))
End Function[code]....
... tells me that the LINQ extensions aren't loaded. Using NHibernate.Linq seems to be made in a way that it's incredibly easy to use, hence there are no tutorials on how to set it up. (Or at least I couldn't find any).
Why Does Linq Lambda Work One Way But Not The Other
Dec 7, 2011I am learning MVC3 and transitioning to VB.NET from C# at the same time (Fun, I know). I am running through the MvcMusicStore sample for learning MVC3. All the samples are in C# so I am converting them to VB. I came across one piece of code that I was unable to directly convert and had to change slightly to get it to work.
why one way works and the other doesn't.
This does not work:
Dim albums = New List(Of Album)() From { _
New Album() With { _
.Title = "A Copland Celebration, Vol. I", _
[Code].....
.net - GroupBy In LINQ To DataSet?
Jul 14, 2011Background: 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.
DBNull When Using LINQ To DataSet
May 20, 2010I'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.
View 1 RepliesGet Work ASP.NET DataSet When Connection Losts?
Jan 12, 2011I made a basic program that connects and gets content from a table via SQL, it's working normally. What I want is; when connection losts via SQL Server or internet connection, it must continue to list items that it got before connection losts instead of giving "Connection Problem Error".[code]...
View 2 RepliesVS 2010 DataGridView To DataSet Won't Work
Aug 7, 2011I' newbie and i dont understand why this won't work TableName is String "Tab"DataGridMain is name of DataGridView.[code]
View 5 Replies.net - LINQ: Except Doesn't Work In The Expected Way
Jul 18, 2011I've problems to detect if there are new rows in a DataTable Email_Total that is yet not imported into ContactDetail.
Dim srcUnique = From row In src.Email_Total
Select row.ticket_id, row.interaction, row.modified_time
Dim destUnique = From row In dest.ContactDetail
[Code].....
.net - Order By Does Not Work With Concat() In LINQ
Aug 8, 2011Using VB.net and the following LINQ statement. I suspect the "Order by" does not work with Concat(). I want to list the current item the user has and then list more available items in asending order. So first i select the current item from the db and then select the next available items in order. LINQ is ignoring the order by statement and sorting by the PK (which is itemID) I examined the list immediately after executing the statement. When I break up the statement and do them separately they work as predicted.
(From items In myDatabase.ItemAssignments _
Where items.BuildingID = buildingID _
And items.ResidentID = ResidentID _
[Code].....
Integer Datatype Not Work In Linq To Sql?
Mar 15, 2011I face a problem that if i make a datattype in sql server of Integer and then use it in linq to sql query it give error of "specific cast not valid" and when i change datatype into varchar the linq to sql query work fine one more thing how to use linq to sql query to make crystal report?
View 2 RepliesWork With Multiple Updates By Linq To Sql?
Sep 11, 2010it is possible to do a multiple records editing by linqtosql method in one click event?What I've been trying to do is to edit all the names in the table which are having the same account number.
Private Sub Button2_Click(------------) Handles Button2.Click
Dim accnt As String
accnt = Textbox1.Text
Dim db As New memrecDataContext()
[code]....
Why is it these codes could only edit records in one datarow?Can you debug the codes to edit all records which are having the same account number after it is being query?
DB/Reporting :: Add LINQ To DataSet To Current App
Jun 4, 2012I 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]
View 7 RepliesGetting Error With DBNull When Using LINQ To DataSet
Nov 12, 2011I'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.
LINQ / Select Distinct From Dataset?
Aug 20, 2010I 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?
LINQ Dataset LEFT JOIN?
Jun 14, 2012i 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]...
LINQ To Dataset - How To Handle DBNull
Jan 29, 2008This 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.
Linq To DataSet Order By Clause
Feb 7, 2012I 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"?
Use Linq As A Data Source Instead Of Dataset?
Apr 19, 2010I 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?
Using Linq For Object Dataset Processing?
May 26, 2011I 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]......
VB Dataset Linq With String Where Clause?
Mar 17, 2009Right 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].....
VS 2008 How To Work With Multiple Updates By Linq To Sql
Oct 19, 2009I would like to ask if it is possible to do a multiple records editing by linqtosql method in one click event? What I've been trying to do is to edit all the names in the table which are having the same account number. I was able to edit but only one name has been edited and the rest are not
******************************************************
Private Sub Button2_Click(------------) Handles Button2.Click
Dim accnt As String
accnt = Textbox1.Text
[Code]....
Why is it these codes could only edit records in one datarow? Can you debug the codes to edit all records which are having the same account number after it is being query?if that is possible for you.
.net - LINQ Null Date Comparison In Dataset?
Aug 26, 2011I 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")
Join Multiple Datatables Using LINQ To Dataset?
Feb 8, 2012I 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].....