c# data matrix generator DATA ACCESS LAYER SERVICES in Visual C#.NET

Generation DataMatrix in Visual C#.NET DATA ACCESS LAYER SERVICES

DataFormatString="{0:$#,###.##}" /> <asp:BoundField DataField="PageCount" HeaderText="Pages" /> <asp:BoundField DataField="ISBN" HeaderText="ISBN" /> <asp:BoundField DataField="PublicationDate" HeaderText="Published" DataFormatString="{0:MM-dd-yyyy}" /> <asp:BoundField DataField="ScanDate" HeaderText="Scanned" DataFormatString="{0:MM-dd-yyyy}" /> <asp:CommandField CancelText='x' UpdateText='ok' ShowEditButton="True" </Fields>

<FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" /> <CommandRowStyle BackColor="#D1DDF1" Font-Bold="True" /> <RowStyle BackColor="#EFF3FB" /> <FieldHeaderStyle BackColor="#DEE8F5" Font-Bold="True" /> <PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" /> <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" /> <EditRowStyle BackColor=CornflowerBlue /> <AlternatingRowStyle BackColor="White" /> </asp:DetailsView> The single most important part of this declaration for this discussion is the DataSourceID property, which points the control at odsBookDetail. This causes the ObjectDataSource control to feed these control instances of BookDetails as they re selected from the ListBox. The BoundField declarations of this control then name public properties of that business object. Figure 11-4 displays the output generated.

Editing is also supported by the data source controls. In the declaration of odsBookDetails, notice that in addition to declaring GetBook as the SelectMethod, you re also declaring UpdateBook as the UpdateMethod. UpdateMethod="UpdateBook" This is another method on the BookBinding class. Let s take a look at this code. public void UpdateBook(BookDetails b) { b.Save(); } Notice the type of the argument that it accepts is BookDetails. This is determined by the DataObjectTypeName property on odsBookDetails. The ObjectDataSource takes care of creating an instance of this type and moving values from the DetailsView to this instance of the business object, before passing it along as an argument to the UpdateBook method. Once in this method, you have only to tell the business object to move its values to persistence. This is work that the business object would usually delegate to a data access layer. As far as the DetailsView is concerned, enabling editing involves a single element used in its declaration. <asp:CommandField CancelText='x' UpdateText='ok' ShowEditButton="True" />

This results in the Edit hyperlink being displayed (as shown in Figure 11-4). When the user clicks this link, the DetailsView automatically transforms its display from read-only into a data entry screen (see Figure 11-5).

Now the user can apply changes, and when she clicks the ok link, the ObjectDataSource automatically creates an instance of the BookDetails object and passes it to the UpdateBook method of the BookBinding object. And you still have no code in the code-behind the EditBook Web Form. As you begin to use these controls to implement real functionality, you ll find yourself in need of tweaking the interaction between these data source controls and the Web Controls they re bound to. Luckily there s a fairly rich event model exposed, enabling you to modify and extend the default behavior of these binding interactions (see Table 11-4). Table 11-4. Events Exposed by the ObjectDataSource Control

Deleting Deleted Filtering Inserting Inserted ObjectCreating ObjectCreated Selecting Selected Updating Updated

Raised before a delete operation is executed Raised after a delete operation has completed Raised before a filter is applied to the underlying control data Raised before an insert operation is executed Raised after an insert operation has completed Enables the developer to create his own custom object for the data source to use in binding operations Raised after the data source s object is created, allowing for custom initialization Raised before a select operation is executed Raised after a select operation has completed Raised before an update operation is executed Raised after an update operation has completed

In our example, the user may change the title of the book when editing. When they update the book, the DetailsView will automatically change back into a read-only view, but the ListBox will not be updated and so the title will be incorrect in the list. You can fix this by using the Updated event of the DetailsView. You can set up this trap with an attribute of the DetailsView declaration: OnItemUpdated="dvEditBook_ItemUpdated" In your code-behind, you can update the displayed value of the selected book: protected void dvEditBook_ItemUpdated( object sender, DetailsViewUpdatedEventArgs e) { lbBookList.SelectedItem.Text = e.NewValues["Title"].ToString(); }