ADO.NET DataAdapter is a bridge between data source and DataSet. The implementation of DataAdapter can be SQLDataAdapter, OLEDBDataAdapter, iDB2DataAdapter etc. DataAdapter.fill method fills data source recordset to a DataSet or DataTable returned by a ‘select’ query.
After populating to a DataSet and DataTable, database connection can be closed but DataTable data still able to access. This is known as Disconnected ADO.Net operation.
We do not have to re-connect to database if we want to retrieve same data with previously DataAdapter.Fill work. We can access the DataTable’s data like an array.
Because of that performance of disconnected operation is better compared with connected one in some cases.
If the ‘select’ query has result of thousands or millions record DataAdapter.Fill method will populate them all thus long run might occur, DataAdapter.Fill looks like slow.
However there is no default method to cancel DataAdapter.Fill. So to terminate long Fill process we have to kill it manually and the application will close.
We need to know how to cancel DataAdapter.Fill on the fly for particular reason.
Posted in Visual Basic .Net
Tagged Abort DataAdapter.Fill, BackgroundWorker, Cancel DataAdapter.Fill, DataAdapter.Fill, DataTable RowChanged, Disconnected operation, SQLCommand, SQLConnection, SqlDataAdapter, VB .Net, Visual Basic
A lot of example of Model View Controller Pattern (MVC) are related to Web application but we can make it on Winform.
As a brief, Model View Controller is a way to separate between bussiness logic and presentation. Each layers are independent from others or loose coupling.
Model layer is a business logic. It can be database access or any business rules. View layer is a application layout design. Controller is a connector between model and view and act as main program at MVC.
Users see a controller in the application. MVC is useful for developing medium to large product with several programmers. Those programmers can work simultanously. They can work independently as much as possible.
I already have simple example of web MVC using php at Web Model View Controller (MVC) Concept with PHP example
In this example I use VB.Net Winform Application and using WebBrowser Control as a user interface. I have earlier post that explain on Using VB.Net WebBrowser Control as WinForm user interface.
I create 3 projects in the solution to represents Model View Controller them self.
The three projects are ClassLibDatabaseMVC.vbproj as Database/Model Layer, ClassLibPresentation.vbproj as View Layer and WinFormBrowserMVC as Controller Layer.
Most application use textbox, frame, picturebox, label, listbox, combobox controls etc to make a user interface.
On the other hand WebBrowser Control commonly used to browse online website. However WebBrowser Control can be used to build rich user interface. We can develop any project i.e database, files, streaming operation.
The requirements are only knowledge of html tags, methods and behaviour of WebBrowser Control itself. In my opinion, it is easier to develop using webbrowser’s html rather than label, textbox, picturebox controls etc
Key points to develop with webbrowser on VB .Net 2010 are: