Two Way Binding LINQ To SQL DataContext Classes
Aug 17, 2009How to bind a textbox in design view to a LINQ to SQL datacontext class?
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LINQ To SQL DataContext To XML With XSD Schema?
Dec 27, 2010I 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].....
Check Whether A Linq-to-SQL Object Is Already Attached To A DataContext?
Jun 27, 2011I 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[,,,,,
DataBinding LINQ DataContext - Add A New Record Since The Textbox's Are Binded To An ISingleResult?
Aug 13, 2009I 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?
View 2 RepliesUse LINQ To Filter Collection Of Nested Classes To Yield Dictionary Of Unique Properties Of Those Classes?
Jan 23, 2012I have two classes, one nested in the other. [code]Neither "Name" or "ID" are unique between operations and records.I wish to construct a dictionary using LINQ = Dictionary(Of String, Of List(Of Integer), whereby the keys are uniqe examples of Names in my collection and the values are the collective set of distinct IDs that are associated with those names.
View 2 RepliesIn A Datacontext Are Inserted Values Not Available Within Datacontext Until After Submitchanges
Mar 18, 2009I'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.
View 3 RepliesWinforms Data Binding: Custom Classes Or Datatable?
Jul 8, 2009Am in the process of architecting a new windows forms application, and I intend to use Visual Basic 2008 and SQL Server Express 2005. This is my first application in .Net and I really want to observe the best OOD & OOP principles to create an application that is easy to maintain and extend (add new functionality). My issue is in regard to databinding on the UI. From experience, what do you guys recommend to use for databinding? Should I return datasets/datatables from my Business Layer and bind these to UI controls or should I return Business Objects and bind these to UI controls? And what are the pros and cons of each approach?
View 1 RepliesLINQ To SQL Classes Not CLS-Compliant?
Aug 5, 2009I'm using LINQ to SQL as my data access layer for a new project.I have added my database tables to the designer and all is well.Whenever I use one of these classes in a function, Visual Studio warns me that 'Type xxxx is not CLS-compliant' or that 'Return type of function xxxx is not CLS-compliant' Is this a problem with the classes that LINQ to SQL generates? Does it matters? Can I disable these warnings anywhere? My VS error list is clogged up with these warnings making it hard to see anything else.
View 4 RepliesDifference In Refreshing Linq To Sql Classes
May 1, 2009what is the difference between these 2 ways to refresh a linq class
1) LinqDB.Refresh
2) LinqDB =
New DataClasses1DataContext
I have got the impression that some time the linqdb.refresh does not work at all
IDE :: Creating LINQ To SQL Classes: Using The O/R Designer?
Mar 27, 2009I am learningCreating LINQ to SQL Classes: Using the O/R Designer, the link is found below[url]...But when I Step #8 of Binding Controls on a Windows Form to Entity Classes says:8. Create an event handler for the Form_Load event by double-clicking the form. Add the following code to the event handler:
View 4 RepliesVB 2008 LINQ To SQL Classes - How To Use App Role
Feb 18, 2010I am curious as to the proper technique to use SQL Server's AppRole with a LINQ to SQL Class. I understand I have to establish the intial connection with no connection pooling. However, do I simply call the SQL stored procedure sp_setapprole using standard LINQ before executing any of my methods that interact with the database, or is there a better way to enable and use AppRole within the LINQ to SQL class?
View 6 RepliesLINQ - Can LinqPad Be Used Runtime Against Populated Classes
Jul 21, 2009VB.net VS2008 My program dynamically populates a class as I click on specific calendar dates runtime. I am currently using various LINQ statements targeting this class for reporting purposes. However, all of my LINQ statements are hard-coded. Are there available solutions / modules which will provide me with a LINQ command and RESULTS window which can be set to an instance of a class so I can experiment with other commands runtime? Can LinqPad be used runtime against populated classes?
View 1 RepliesLate Binding In Linq?
Aug 26, 2010I have a simple LINQ query that is going against a collection.
Dim oList = From w In Os
Order By w.ClassTitle Descending
Select w
[code].....
Convert These 4 SQL Tables Into OO Classes (Java Or C#) But Not With NHibernate/LINQ?
Apr 21, 2012I am trying to learn OOD/OOP and read on the net that I am not supposed convert SQL tables into classes. But I cannot find an explanation why not to do it or which tables to skip. So I made an web application based on the below diagram. It works perfectly well. But I do not use OO. which table should not be mapped into a class and why not. do not use LINQ or NHibernate, etc as I do not understand them. I just need to understand the OOD.
View 2 RepliesLinq To XML Binding Into A Winform Datagrid
May 14, 2009I have a really simple xml:
dim myXml as XDocument = _
<?xml version="1.0" encoding="utf-8"?>
<root>
<RecordNumber id="1">
[Code].....
I get element information and the data in my grid. Plus the grid is showing the columns of data as rows.
I got this idea from the Beth Massi show, but She use Linq to SQL, (which looked really easy). So I thought, well, what the heck, its all iEnumarable...
Asp.net - Binding Different LINQ Datasource Using Same Variable W/ If Statement?
Nov 27, 2010OK So I know WHY I am having the error I am getting. I don't know HOW to fix it. Basically, if the user doesn't have a certain permission, I need to join another table. But .NET is so picky I can't just make two different queries in an IF statement and then use it outside of the if statement. I can think of some ugly work arounds for this, but I would rather not. I am fairly new to .NET I know just enough to be dangerous.
[Code]...
because of this: Dim l As IEnumerable(Of Company) its not just IEnumerable of a Company, its got the source in it. I have to explicitly select source to use it in my datagrid. Can I make Dim l something that will make it stop complaining?
C# - Entity Framework/LINQ To SQL Data Binding Use Reflection?
Apr 20, 2009I'm taking a peek at both the Entity Framework and LINQ to SQL, and while I like the systems (and of course the LINQ integration) I'm a little skeptical on the data-binding aspect. I've taken query results and inspected them, and they don't appear to implement the standard .NET list-binding interfaces (IBindingList, and more importantly ITypedList), leading me to believe that binding them to a grid (or anything else) is going to use reflection to get/set my entity properties. This seems like a comparatively expensive operation, especially when all of the code is generated anyway and could implement the interfaces. Is reflection used to get/set the value of the properties?
Edit: I'm actually concentrating on whether or not ITypedList is implemented somewhere along the way, as that's what has the capability to provide an explicit mechanism for defining and interacting with properties without resorting to reflection. While I didn't have a LINQ to SQL project up,I did inspect a simple Entity Framework entity query result, and it did not appear to implement ITypedList.
Edit 2: After accepting Marc's answer, I thought it might be helpful for others if I posted some simple code I used to seamlessly implement his solution. I put the following in the static constructor for my class:
public static ContextName()
{
foreach(Type type in System.Reflection.Assembly.GetExecutingAssembly()[code]....
While this is for LINQ to SQL, I'm sure an equivalent version could be written for the Entity Framework. This will scan the assembly for any types with the Table attribute and add a custom provider for each of them.
Cannot Filter A Binding Source Based On A Linq Query
Feb 3, 2010I've got a datacontext and created a binding source using LINQ to sql but cannot filter said bindingsource. The supportsfilter of the bindingsource is set to false ? why ? I can't find any info to say that I cannot filter a binding source based on a linq query.[code]
View 3 RepliesAsp.net - Late Binding Operations Cannot Be Converted To An Expression Tree With LINQ?
Jul 26, 2010I currently have a View in MVC where I pass a single set of data to the view. However, I've come across a problem where I am having to use a LINQ query within a For Each loop in the View to pull out additional information from a SQL View of data from another DB.
The error I'm getting is Late binding operations cannot be converted to an expression tree.
The particular snippet I'm encountering the error on is:
[Code]...
Implement The .Find Method When Binding A BindingSource To LINQ (IEnumerable) Result?
Mar 15, 2008I'm binding a DataGridView to a BindingSource to a LINQ IEnumerable, I found that the BindingSource.Find method throws an exception because .Find isn't implemented in IEnumerable (and the BindingSource just passes the call to it's DataSource). I need to use BindingSource.Find to select/highlight a particular row in the DataGridView.
Is there a feasable way to extend my DataContext to support this behavior w/o breaking anything else? I expected to find the code out there already, but I've searched exaustively with no luck.Without it, I cannot "move" the BindingSource using .Position and that's a pretty common use of the BindingSource I think.
Get Data From MenuItem.DataContext?
Dec 15, 2011I 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]...
Overriding Datacontext For View?
Mar 15, 2012I 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.
View 1 RepliesDataContext - Discard Changes Of Only One Record In Table
Apr 1, 2010I 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?
View 3 RepliesDifference Between Using DataContext Class And SqlConnection?
Mar 2, 2012I 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?
View 1 RepliesUnderstanding ItemsSource And DataContext In A DataGrid?
Jun 14, 2010UPDATE: 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.
View 2 RepliesSetting The DataContext On An Entity Instance After It's Retrieved?
Apr 14, 2011I'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]....
Setting User Control's DataContext From Code-Behind?
Jul 8, 2009This 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].....
Using Same Connection String In A DataContext Constructor And SqlConnection?
Oct 4, 2011I am preparing to deploy a web service that uses SqlConnection primarily as its means to get to the database, and I am adding some new methods that use a DataContext instead of thatand the default constructor and DBML file would use a connection string refering to my development machine (I believe...)
View 1 RepliesWpf - DataContext Issues With ListBox After Changes To MainWindow.xaml?
Jun 18, 2012I am new to WPF and the MVVM design pattern this month, and more than a little out of practice in general. To learn, I've been playing around with textboxes, rectangles, and ways to display them in a window. I began with Ashley Davis' excellent "Simple Drag Selection in WPF" tutorial, which walks through creating a view model for a collection of rectangles, binding a listbox to said collection, and styling the listbox with a canvas, creating a data template for the rectangles, as well as basic "rubber band" selection logic.
I have since built on this tutorial to improve the drag selection so that it behaves much more like selection does in windows explorer, and to allow resizing the rectangles from the corners or edges.All was well until I changed the MainWindow.xaml in an effort to include a column on the side for various buttons and controls, thus moving the "editor surface" grid from inside a 1x1 grid on the main window to a column of a 1x2 grid, moving the data template to the grid's resources (since it will be the only element in the window that needs it). As soon as I did this, subroutines that I wrote which interact with the listbox started misbehaving--rubber band selection no longer works. There's no visual indication that listbox items are being selected (they were highlighted previously), and interrogating listBox.SelectedItems.Count after a drag-selection mouseUp event returns a zero.
After some experimentation, reading many questions on this site and sections of my WPF Unleashed book, and going over the msdn databinding overview, as of this morning I still cannot find my mistake(s). I believe it is a data binding mistake or incorrect data context.Some details about the view models involved:
DataFieldViewModel
...implements INotifyPropertyChanged and exposes properties for its (in this case a rectangle and a textbox) X,Y position, width, height, visibility, and selection status (a way to track it across several rubber band selection operations)
PageViewModel
...implements INotifyPropertyChanged, and has among other things an ObservableCollection of type DataFieldViewModel, called DataFields, and exposes it as a ReadOnly Property.Here's a look at MainWindow.xaml.vb and one of the broken subs:
Namespace EditorUI
'
' The main window of the editor.
[code]....
V B 2008 Express Book - Can't Connect To The "Service-Based Data Base" Or To The "Linq To Sql Classes"
Jan 6, 2010I can't connect to the "Service-Based Data Base" or to the "Linq To Sql classes". I tried all that I've read in the Forums for days : ( I removed the VB 2008 and SQL 2205-2208, then upload VB 2008 from my CD only. I'm starting a Web Technology class in 2 weeks, and the complition of the book is my entry requirement.
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