How to: Allow an Administrator to Create Custom Persistent Fields in an XPO-Based Application
5 min to read
You can allow an application administrator to create custom persistent fields and display the added fields' data in the UI without recompiling the application. In this example, the SkypeID field will be added to the Contact business object in the MainDemo application.
The following sections describe the process of implementation custom persistent fields from application settings to runtime customization.
With this configuration, your application loads information on custom persistent fields from the database and then updates the database schema. However, a thread-safe data layer does not support altering the data model after the database connection is established.
Copy the DBUpdater.v19.2.exe and DBUpdater.v19.2.config files from the %PROGRAMFILES(x86)%\DevExpress 19.2\Components\Tools\eXpressAppFramework\DBUpdater\ folder to the application's installation folder.
Choose the Model Editor Type
It is necessary to determine which type of the Model Editor is appropriate for your application: standalone or built-in.
A built-in Model Editor
When an administrator uses a WinForms application, it is possible to invoke the built-in Model Editor tool to add a custom field to the application model. Using this Model Editor type, the administrator can edit both Model Differences stored in the application database and Model Differences from the XAFML file.
A standalone Model Editor
The use of the standalone Model Editor is preferred if an administrator uses only an ASP.NET application and Model Differences are stored in the XAFML file. For information on how to use this tool, refer to the Deploy and Run the Standalone Model Editor section of the Ways to Invoke the Model Editor topic.
Implement the Persistent Field and Display It
Follow the steps below to add a custom persistent field at an end-user workstation.
Invoke the built-in Model Editor using the Tools | Edit Model command at runtime or close the application and start the standalone Model Editor by running the DevExpress.ExpressApp.ModelEditor.v19.2.exe executable file.
If you use the standalone Model Editor, specify the path to the application configuration file (e.g., MainDemo.Win.exe.config or Web.config) and click Open in the Open Model dialog.
Navigate to the BO_Model | Contact node in the tree on the left. Right-click the OwnMembers child node and choose Add... | Member.
Set the Name property of the newly added node to "SkypeID". Then, set the IsCalculated property to "False", Type to "System.String", Size to "32", and Caption to "Skype ID".
If the built-in Model Editor is in use, copy the differences that you have introduced in the administrator's layer using the Merge Differences command. Otherwise, skip this step and move to the next one.
Save changes using the Save button or the CTRL+S shortcut and restart the Model Editor.
Navigate to the Views | Contact_DetailView node in the tree on the left. Right-click the Items child node and choose Add... | PropertyEditor.
Set PropertyName and Id to "SkypeID".
Focus the Layout node. Right-click the empty space within the form preview displayed on the right and select Customize Layout.
Drag the Skype ID item from the invoked Customization window to an appropriate position within the form.
Restart the application and open the Contact Detail View to see the result demonstrated in the introduction of this topic.
If the application is installed on several PCs and the Administrator's Model Differences are stored in the Model.xafml file, copy it from the application's working folder to each PC. Otherwise, the created field will be available only at the workstation where you added it.
Apply Changes to the Database
Use the DBUpdater tool to add the column mapped to the newly created custom persistent field to the database.
Open the Command Prompt, change the current directory to the applications working directory, and run the following command.