XafApplication.CustomCheckCompatibility Event
Occurs when trying to access the application’s database (when logging on or creating an Object Space).
Namespace: DevExpress.ExpressApp
Assembly: DevExpress.ExpressApp.v23.2.dll
NuGet Package: DevExpress.ExpressApp
Declaration
Event Data
The CustomCheckCompatibility event's data class is CustomCheckCompatibilityEventArgs. The following properties provide information specific to this event:
| Property | Description |
|---|---|
| ApplicationName | Specifies the application’s name. |
| Handled | Gets or sets a value that indicates whether the event handler has completely handled the event or whether the system should continue its own processing. Inherited from HandledEventArgs. |
| IsCompatibilityChecked | Indicates whether a compatibility check has already been performed. |
| Modules | Lists all Modules used by the application. |
| ObjectSpaceProvider | Specifies the Object Space Provider to be used for compatibility checking purposes. |
Remarks
The CustomCheckCompatibility event is raised as a result of the XafApplication.CheckCompatibility method call. Handle this event to perform a custom check of the application and database compatibility, update the database, or any other action. Use the handler’s CustomCheckCompatibilityEventArgs.ApplicationName parameter, to compare the actual application name and the application name written in the database. To compare the actual versions of the application’s modules and the ones written in the database, use the handler’s CustomCheckCompatibilityEventArgs.Modules parameter. Use the CustomCheckCompatibilityEventArgs.ObjectSpaceProvider‘s methods to create a Session or an Object Space, to work with the database. Set the handler’s Handled parameter to true, to cancel executing default actions. By default, if the application is being run in the debugging mode, the XafApplication.DatabaseVersionMismatch event is raised. Otherwise, the database and application compatibility is checked. If the database cannot be opened or its version is older than the actual application version, the XafApplication.DatabaseVersionMismatch event is raised.
Note
The CustomCheckCompatibility event is raised many times. So, database-intensive checking should only be performed on the first compatibility check, when the CustomCheckCompatibilityEventArgs.IsCompatibilityChecked property returns false.
XAF uses the first registered Object Space Provider for the following purposes:
- To get XafApplication.ObjectSpaceProvider and XafApplication.ConnectionString property values.
- To pass this Provider as the CustomCheckCompatibilityEventArgs ObjectSpaceProvider argument.
- To update an application.
Ensure that NonPersistentObjectSpaceProvider is not the first registered Provider in your application.
Note that in applications with the Application Builder, you need to use the Application Builder’s ObjectSpaceProviders property to register Object Space Providers instead of the XafApplication.CreateDefaultObjectSpaceProvider method or XafApplication.CreateCustomObjectSpaceProvider event to register Object Space Providers. Refer to the following help topic for more information on how to do this: Integrate Application Builders into Existing Applications.
We strongly recommend this because the use of the XafApplication.CreateDefaultObjectSpaceProvider method and XafApplication.CreateCustomObjectSpaceProvider event conflicts with IObjectSpaceFactory and IObjectSpaceProviderFactory service usage.
This technique also improves performance of your application because the application instance is not created in this case.
Related GitHub Examples
The following code snippet (auto-collected from DevExpress Examples) contains a reference to the CustomCheckCompatibility event.
Note
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