Difference Between Using DataContext Class And SqlConnection?
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?
View 1 Replies
ADVERTISEMENT
Oct 4, 2011
I 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 Replies
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.
View 3 Replies
May 15, 2009
I can't make difference between public class and private class and friend and protected friend class.
View 1 Replies
Mar 4, 2011
explain to me the differences between an abstract class and a class marked MustInherit?
Both can implement shared and instance constructors and logic. Both can/must be inherited.
So why use one over the other and what is the difference?
Edit: Sincerely apologize I have got my languages mixed up. Will mark correct answer as soon as I am allowed.
View 2 Replies
Oct 30, 2010
What is the difference between Private Sub /private Function / Private Class and to use them?
View 4 Replies
Nov 25, 2010
I'm using vb10. I need to use a timer for forms to turn off and on and I was going to use a timer control and I noticed there is a timer class. What is the difference? Should I use the timer class instead?
View 5 Replies
Jun 29, 2010
When we can access the public methods via object then why is there need of inheritance.
View 2 Replies
Nov 4, 2011
Whats the difference between these two initialization methods for obj? I've seen both of these, but know know if there is an appropriate time to use one vs the other. I found this post which covers C#, but not sure if the same applies to VB.Net.[code]
View 3 Replies
Dec 17, 2009
what's the main difference between a Class and a Type and a ValueType.and is a Delegate a Type? or an eventhandler/event (the actual event itself)is every object a type? or is it only true in VB
View 3 Replies
Aug 6, 2009
What's the difference? I'm going to create a password encrypting program, and I wanted to know what's the basic difference about the managed class and the "not managed" class.
View 4 Replies
Dec 18, 2010
while reading a book i encountered the use of a statement in asp.net(with vb as code language)dim myReader as OracleDataReader(declared as global variable)[Correct]however by mistake i used code as shown below [code]it's workin correct when using OracleDataReader without brackets(as earlier in book)I just want to know the difference between oracleDatarReader and OracleDataReader().
View 4 Replies
Apr 26, 2011
So I was assigned to create a calculator that can calculate the sum, product, difference, & quotient using an external class. Unfortunately my teacher isn't exactly the best and I'm new to VB, I know how to create a calculator in VB .NET but when it comes to external classes,
View 3 Replies
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]...
View 3 Replies
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].....
View 1 Replies
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.
View 1 Replies
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?
View 3 Replies
Aug 17, 2009
How to bind a textbox in design view to a LINQ to SQL datacontext class?
View 3 Replies
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.
View 2 Replies
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[,,,,,
View 1 Replies
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]....
View 2 Replies
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].....
View 3 Replies
Jun 18, 2012
I 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]....
View 1 Replies
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?
View 2 Replies
Mar 20, 2011
System.Collections.Specialized contains StringDictionary
[url]...
What's difference with Strong Typed Dictionary in Generics?
View 1 Replies
Mar 3, 2009
my old vb6 program used to store to ini files now with .net I rekon I need to do something new.. was thinking XML but then in searching around I stumbled apon this my.settings stuff.. so I followed the instructions but something strange is going one..
1. whats the difference between the standard my.settings and adding a new class that is of settings ? anything ?
2. I made 10 new settings in the setting manager but when I try to change then it gives me the old squiggle line saying no go.
View 15 Replies
Mar 12, 2010
What is the difference between using the 'array' class in VB and just declaring an array like normal. In other words, what is the difference between:
Dim numOfTicketsPerDay As Array
Dim intNumOfTicketsPerDay(6)
As Integer
Is there any preference of when one should be used over another?
View 2 Replies
Jan 13, 2011
I am trying to update some code. I have a vb file that begins with this...
Imports System.Data.SqlClient
Imports System.Data.Sql
Imports System.Data.SqlTypes
[Code].....
...and it accepts it. Why do I need to explicitly write out System.Data.SqlClient every time I use an object from that class???
View 4 Replies
May 17, 2010
i would like to know if there's something wrong in this asp.net code:
mydatareader = mycmd.executeReader()
if myDataReader.HasRow then
// Do something
[code].....
View 4 Replies
Jul 20, 2011
I am confused about something and I hope someone here can give me an answer
View 3 Replies
