Check Whether A Linq-to-SQL Object Is Already Attached To A DataContext?
Jun 27, 2011
I have an object that may have been inflated via a plain old DataContext, or may just have been new-ed up with just its .ID property set. There's no way to know for sure. I'm looking to rehydrate the entire object from whatever is in the database. If the object was new-ed up, I can call .Attach() on the table object and refresh from the Data Context with no trouble. But, if the object was already inflated from the DataContext I get the error: "Cannot attach an entity that already exists.". There's no timestamp field or anything like that - just an integer primary key being used to control the rehydration. I'd like to know if there's a way to conditionally attach. Here's the code - it works the way I want it to, but this seems a hackish way to go about it:
' myDC is a shared instance of a vanilla DataContext...
' myObj is an instance of a linqed-up `SomeLinqObject`
Dim tbl = myDC.GetTable(Of SomeLinqObject)()
[Code[,,,,,
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Dec 27, 2010
I have some data in my Linq.DataContext.I had succes in converting it to an XSD - Schema, using the following code:
Dim changeset As System.Data.Linq.ChangeSet = c.GetChangeSet()
Dim objDic As New Dictionary(Of System.Type, List(Of Object))
If Not changeset Is Nothing AndAlso Not changeset.Inserts Is Nothing AndAlso Not
[code].....
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Aug 17, 2009
How to bind a textbox in design view to a LINQ to SQL datacontext class?
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Aug 13, 2009
I have a LINQ to SQL DataContext with all my tables and all my stored procedures in it. Let me first start off by saying that we are upgrading our project from an access project to a WPF project. So in the Access project you could set a forms datasource to a stored procedure and edit and add new information. So in my WPF project on the page load I call my stored procedure to return an ISingleResult and then call a function to set the binding on every single textbox on the form. One is there an easier way to do this and two what if I want to add a new record since the textbox's are binded to an ISingleResult?
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Mar 18, 2009
I'm going through an XML file of articles and the journalist(s) that wrote them. As we are adding the articles into _Data our datacontext we may come across a journalist that needs adding so we do this: [code] However subsequently we may come across this same journalist again and nothing is returned when we do this: [code] So it uses the code above again to insert the same journalist again.Once all of our inserts are done we do a submitchanges. At this point it has a head fit:INSERT statement conflicted with COLUMN FOREIGN KEY constraint 'FK_ articles_ journalists_journalists'. The conflict occurred in database 'blah', table 'journalists', column 'id'. The statement has been terminated.From looking through the sql generated in sql profiler you can see that it is trying to add some journalists more than once, this will fail as the name must be distinct. The subsequent records that are trying to be inserted with these journalists are failing as the journalist wasn't updated.Surely if I have a collection of journalists, add some to it and then look in my collection I should see all of them and not just the original ones.
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May 2, 2010
I know how to display attached modules but how do i check if a file is locked by a dll.
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Dec 19, 2010
I read from a text file to see what I need to add to my MenuStrip. Each line in the text file is a new item. When I read I add the new item's OnClick event using AddHandler to get its text when it's clicked. Here are my two subs[code]....
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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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Nov 2, 2009
I am having trouble with this piece of code. This is an event when a check box is clicked. It gives me an error "Object Reference Not Set To a Instance Of An Object"I am gathering that something here needs to be AS NEW something but I have tried a few things and can not get it straight.
If Me.ckbDefault.Checked = True Then
Dim current_indexno As Integer
current_indexno = Nothing[code]....
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Dec 15, 2011
I have a context menu on my DataTemplete for a list box, and that menu will contain links to Favourite and Retweet the tweet (the menu item) But I don't know how to get the information about the Tweet in code. I am trying the following Line:
[Code]...
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Mar 15, 2012
I am setting my viewmodel as datacontext in my xaml but I override it to my view to make few functions work however to achieve the visibility on some grids and I have a property in my VM can I override my datacontext back to my VM? If so how? I have a stackpanel that has datacontext overriden as my grid and within that stackpanel I need to change the datacontext for a button.
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May 27, 2011
I have an object that looks like follows:
Public Class MyObject
Public Property Key as Intger
get 'Elided for clarity
[code].....
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Oct 11, 2011
I have a list of objects, each with 2 relevant properties: "ID" and "Name". Lets call the list "lstOutcomes".I need to check the list for duplicates (meaning object1.ID = object2.ID, etc.) and set a flag (valid = false, or something) if there is at least one duplicate. Also, it would be nice to send a message to the user mentioning the "Name" of the object, when it fails.I am sure I will need to use the Group By operator to do this, but I am not used to doing that in LINQ, and the examples out there are just not helping me. This article seems to be close to what i need, but not quite and it's in C#.
Here is a starting stab at it...
Dim duplist = _
(From o As objectType In lstOutcomes _
[code]......
help?
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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 1, 2010
I would like to know if its possible to discard changes of only one record of only one table in datacontext. I use databind to bind my controls on a form. I modify one record at a time. after the modification, the user have to hit save button to validate. But he can hit cancel. I would like that the cancel button discard all the changes that the user has done. Is it possible?
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Mar 2, 2012
I asked a question earlier where I was told a simple way to "bind data to objects" is to just run a SqlConnection(connectionString). The response also included a comment saying I could get fancy with L2S and Entity Frameworks, so I looked deeper into those. It seems all you have to do with the DataContext object is point to the database. Why would SqlConnection be a benefit? What is the difference (or pros/cons) of using either one of these? Is one more "standard"? Is one more modern?
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Jun 14, 2010
UPDATE: See the bottom of this question for what I did to solve the problem.I'm trying to understand how the ItemsSource and DataContext properties work in a Silverlight Toolkit DataGrid. I'm currently working with dummy data and trying to get the data in the DataGrid to update when the value of a combo box changes.
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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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Mar 18, 2010
I can't quite figure out why this Linq Statement isn't working as i would expect:
[Code]....
I would assume that this would create a new collection of anonymous types, that would be distinct. Instead it creates a collection the size of the "ThisParentCollection" with duplicate "MyAnonymousType" in it (duplicate id's).
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May 28, 2009
So say I have a collection of Bloops
Class Bloop
Public FirstName
Public LastName
[Code]....
Is it possible using Linq to select the FirstName and LastName out of all the Bloops in the collection of Bloops and return a collection of Razzies? Or am i limited to a For-Loop to do my work?
To clear up any confusion, either VB or C# will do. Also this will probably lead to me asking the question of (What about using a "Where" clause).
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Mar 24, 2011
In VB.Net class, I have a JSON data as string. I want to convert them to LINQ class Object.[code]....
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Feb 24, 2010
from a list, which got 3 attributesI want to return a new list of that class where attribut1 recurrence in the list equals Xfor an example this;
1,a,b
1,c,d
1,e,f
[code]....
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Apr 13, 2011
I am using LINQ - VB.Net I want to filter my List object by passing String object in the where.
Dim _permittedTransactionCodes As List(Of String) = Nothing 'String object
it is populated with data.
Dim tap100transCodeInfos As List(Of Tap100transCodeInfo) = _dal.GetActiveTap100transCodeByHdrScreenCde(UCase(screenId), "TRAN_CDE")
i am trying something below, but not getting the filtered results
tap100transCodeInfos.Where(Function(x) _permittedTransactionCodes.Contains(x.TranCde))
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Nov 11, 2010
I am trying to use a simple LINQ to Objects query.When I try to run my application I get the message:
System.InvalidOperationException was unhandled Message="An error occurred creating the form. See Exception.InnerException for details. The error is: Method not found: 'Void sharatTashlumimWS.paymentDetailsManager.set_ReleaseDate(System.DateTime)'."
Source="WindowsApplication1"
StackTrace:
[Code]...
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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 1, 2012
I'm trying out some LINQ expressions and can't get them to work with the List class. Basically I want to be able to sort a list of custom objects by property type, however the C# LINQ syntax is KILLING me and I can't figure out how to convert it to VB
Class Foo
Sub New(Name As String, Position As Integer)
Me.Name = Name
[code]....
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Apr 14, 2011
I'm trying to find a way to have the DataContext available from within Entities.
I want to do something like this:
partial public class MyEntity
public DataContext as MyDataContext
private sub OnLoaded()
[Code]....
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Jul 8, 2009
This should be pretty easy, but it throws VS2008 for a serious loop.I'm trying out WPF with MVVM, and am a total newbie at it although I've been developing for about 15 years, and have a comp. sci. degree. At the current client, I am required to use VB.Net. I have renamed my own variables and removed some distractions in the code below, so please forgive me if it's not 100% syntactically perfect! You probably don't really need the code to understand the question, but I'm including it in cas.
I have a very simple MainView.xaml file:
<Window x:Class="MyApp.Views.MainView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
[code].....
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