c# .net core barcode generator

c# .net core barcode generator

c# .net core barcode generator

The New Web Site window allows you to specify three details: Template: The template determines what files your website starts with Visual Studio supports two types of basic ASPNET applications: website applications and web service applications These applications are actually compiled and executed in the same way In fact, you can add web pages to a web service application and can add web services to an ordinary web application The only difference is the files that Visual Studio creates by default In a web application, you ll start with one sample web page in your project In a web service application, you ll start with a sample web service Additionally, Visual Studio includes more sophisticated templates for certain types of sites, and you can even create your own templates (or download third-party offerings) Location: The location specifies where the website files will be stored.

You ll use this approach to solve a common problem in the section The Limits of the Data Source Controls later in this chapter. In fact, to get really adventurous you could set the ConflictDetection property to ConflictOptions.CompareAllValues so that the old and new values are submitted in the UpdateParameters collection. You can then examine these parameters, determine what fields have changed, and call a different method (with different parameters accordingly). Unfortunately, this isn t a zero-code scenario, and you might end up writing some awkward code for updating and removing parameters. Still, it gives you a valuable extra layer of flexibility.

Typically, you ll choose File System and then use a folder on the local computer or a network path However, you can also edit a website directly over HTTP or FTP (File Transfer Protocol) This is occasionally useful if you want to perform live website edits on a remote web server However, it also introduces additional overhead Of course, you should never edit a production web server directly because changes are automatic and irreversible Instead, limit your changes to test servers Language: The language identifies the NET programming language you ll use to code your website The language you choose is simply the default language for the project This means you can explicitly add Visual Basic web pages to a C# website, and vice versa (a feat that wasn t possible with earlier versions of Visual Studio).

Earlier, you saw an example that allowed users to browse a list of cities in different regions using two linked controls a DropDownList and a GridView. Best of all, this example could be created using a SqlDataSource or an ObjectDataSource; either way, it doesn t require any custom code. Figure 9-9 shows this example. As convenient as this example is, it presents a problem that s difficult to fix. Because it s impossible to create a drop-down list that doesn t have a selected item (unless it s empty), the first city in the list is automatically selected. Many web applications use a different behavior and add an extra item at the top of the list with text such as (Choose a City) . Selecting this first item has no effect. Additionally, you might want to add an item that allows you to see every city in a single list. Figure 9-13 shows the result you want.

So far, all the examples you ve seen have used parameters to supply values to an update operation. However, you can also create a parameter to return a result. With the SqlDataSource, you can use this option to get access to an output parameter. With the ObjectDataSource, you can use this technique to capture the return value. To see this in action, it s worth considering the InsertEmployee() method, which adds an employee record and returns the newly generated unique ID value as an integer: Public Function InsertEmployee(ByVal emp As EmployeeDetails) As Integer ... End Function You don t need to use the identity value. As you ve seen already, linked data controls are bound after any updates are committed, which ensures that the updated information always appears in the linked controls. However, you might want to use the identity for another purpose, such as displaying a confirmation message. To capture this identity value, you need to define a parameter: <asp:ObjectDataSource ID="sourceEmployees" runat="server" TypeName="DatabaseComponent.EmployeeDB" DataObjectTypeName="DatabaseComponent.EmployeeDetails" SelectMethod="GetEmployees" InsertMethod="InsertEmployee" OnInserted="sourceEmployees_Inserted"> <InsertParameters> <asp:Parameter Direction="ReturnValue" Name="EmployeeID" Type="Int32" /> </InsertParameters> </asp:ObjectDataSource> Now you can retrieve the parameter by responding to the Inserted event, which fires after the insert operation is finished: Protected Sub sourceEmployees_Inserted(ByVal sender As Object, ByVal e As ObjectDataSourceStatusEventArgs) If e.Exception Is Nothing Then lblConfirmation.Text = "Inserted record " & e.ReturnValue.ToString() End If End Sub