Tutorial 5 - An ASP .NET Application for Data Editing

• Aug 01, 2019
• 4 minutes to read

Task

To create a simple ASP.NET application to view and edit customer details.

 

Solution

• Define a Persistent Object Class
• Connect to a Database Server
• Retrieve Data Using the XpoDataSource Component

Define a Persistent Object Class

Once a new project has been created, we need to define a persistent object class. To do this, the new class is added to the project. Make it the Customer class.

The FirstName, LastName and Company properties of this class represent the values of the corresponding fields in a database table.

Please note that the property implementations in this sample don’t have all code in their setters that we recommend. We have shortened the sample code for brevity and simplicity. Follow our tutorials to learn the recommended way of implementing property setters.

C#

using DevExpress.Xpo;

public class Customer : XPObject {
    public Customer(Session session) : base(session) {}
    public string FirstName;
    public string LastName;
    public string Company;
}

VB.NET

Imports DevExpress.Xpo

Public Class Customer 
    Inherits XPObject
    Public Sub New(session As Session)
        MyBase.New(session)
    End Sub 
    Public FirstName As String
    Public LastName As String
    Public Company As String
End Class

Connect to a Database Server

Connect XPO to a database server. To do this, create an IDataLayer object. The code which creates the data layer must be placed inside the Application_Start event handler in the Global.asax module of your Web Site. For more information, see Connecting XPO to a Database Server (ASP.NET).

C#

void Application_Start(object sender, EventArgs e) {
    // Code that runs on the application startup
    // Specify the connection string, which is used to open a database. 
    // It's supposed that you've already created the Comments database within the App_Data folder.
    string conn = DevExpress.Xpo.DB.AccessConnectionProvider.GetConnectionString(
      Server.MapPath("~\\App_Data\\Customer.mdb"));
    DevExpress.Xpo.Metadata.XPDictionary dict = new DevExpress.Xpo.Metadata.ReflectionDictionary();
    // Initialize the XPO dictionary.
    dict.GetDataStoreSchema(typeof(Customer).Assembly);
    DevExpress.Xpo.XpoDefault.Session = null;
    DevExpress.Xpo.DB.IDataStore store =
    DevExpress.Xpo.XpoDefault.GetConnectionProvider(conn, 
    DevExpress.Xpo.DB.AutoCreateOption.DatabaseAndSchema);
    DevExpress.Xpo.XpoDefault.DataLayer = new DevExpress.Xpo.ThreadSafeDataLayer(dict, store);
}

VB.NET

Sub Application_Start(sender As Object, e As EventArgs)
   ' Code that runs on the application startup
   ' Specify the connection string, which is used to open a database. 
   ' It's supposed that you've already created the Customer database within the App_Data folder.
   Dim conn = DevExpress.Xpo.DB.AccessConnectionProvider.GetConnectionString( _
     Server.MapPath("~\App_Data\Customer.mdb"))
   Dim dict As New DevExpress.Xpo.Metadata.ReflectionDictionary()
   ' Initialize the XPO dictionary.
   dict.GetDataStoreSchema(GetType(Customer).Assembly)
    DevExpress.Xpo.XpoDefault.Session = Nothing
   Dim store = DevExpress.Xpo.XpoDefault.GetConnectionProvider(conn, _
    DevExpress.Xpo.DB.AutoCreateOption.DatabaseAndSchema)
   DevExpress.Xpo.XpoDefault.DataLayer = New DevExpress.Xpo.ThreadSafeDataLayer(dict, store)
End Sub

Retrieve Data Using the XpoDataSource Component

Persistent objects are retrieved from a database using the XpoDataSource component. After we have declared the Customer class, it’s necessary to rebuild our solution, drag the XpoDataSource component from the Toolbox and drop it onto the page. Then, assign our persistent class to the TypeName property as shown below:

Link the XpoDataSource component to a session:

C#

Session session1;
protected void Page_Init(object sender, EventArgs e) {
    session1 = new Session();
    // ...
    XpoDataSource1.Session = session1;
}

VB.NET

Dim session1 As Session
Protected Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init
    session1 = New Session()
    ' ...
    XpoDataSource1.Session = session1
End Sub

To display data, you need to assign the XpoDataSource component to a control used to represent data. In this example, we use our ASPxGridView component. The image below shows how to bind the XpoDataSource to the grid.

After the XpoDataSource has been bound to the grid, the grid automatically generates data columns for all persistent properties (fields in a table). Enable data editing as shown below:

Finally, add records to the Customer table and run the project.

C#

Session session1;
protected void Page_Load(object sender, EventArgs e) {
    session1 = new Session();
    if (session1.FindObject<Customer>(null) == null) {
        Customer cstm = new Customer(session1);
        cstm.FirstName = "John";
        cstm.LastName = "Doe";
        cstm.Company = "Doe Enterprises";
        cstm.Save();

        cstm = new Customer(session1);
        cstm.FirstName = "Sam";
        cstm.LastName = "Hill";
        cstm.Company = "Hill Corporation";
        cstm.Save();
    }
    XpoDataSource1.Session = session1;
}

VB.NET

Private session1 As Session
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    session1 = New Session()
    If session1.FindObject(Of Customer)(Nothing) Is Nothing Then
        Dim cstm As New Customer(session1)
        cstm.FirstName = "John"
        cstm.LastName = "Doe"
        cstm.Company = "Doe Enterprises"
        cstm.Save()

        cstm = New Customer(session1)
        cstm.FirstName = "Sam"
        cstm.LastName = "Hill"
        cstm.Company = "Hill Corporation"
        cstm.Save()
    End If
    XpoDataSource1.Session = session1
End Sub

The animation below shows the result.

A user can view and edit data in the grid. You don’t have to write any code to save data: all changes are automatically persisted with the next post-back to the server.

 

Results

• We’ve created a simple ASP.NET application that allows end-users to view and edit customer details. Data is stored in the MS Access database (Customer.mdb) which resides in the App_Data folder.
• We’ve declared the Customer class whose instances represent records in the Customer table.
• You learned how to use the XpoDataSource component.