How to: Handle Data Events

You can customize your application by writing code that runs when certain data events happen. For example, you can write code that will run when rows of data in a table are created, accessed, modified, or deleted. You can also write code to verify that a user has permission to modify the data source.

The events you can handle can be grouped into six categories:

• General methods that are run when data is created, deleted, or modified.

• Access control methods that are run when data is created, deleted, or modified.

• Query methods that are run when a data source is queried.

• Query access control methods that are run prior to a query executing.

• Data source methods that are run when a data source is saved to.

• Property methods that are run when a property is modified.

A description of these methods appears in the tables at the end of this topic.

To handle a data-related event

1. In Solution Explorer, double-click an entity or table.

   The entity or table opens in the Data Designer.

2. On the command bar in the Data Designer, click the arrow next to the Write Code button, and then select a method that you want to override. The methods that can be handled by your application appear in the tables below.

   Note

   The Property Methods will only appear in the Write Code dropdown list if a property is selected in the Data Designer.

   The Code Editor opens.

3. Place your cursor in the method that was just created and type the code that you want to run when the event occurs.

List of Data-Related Events

The following tables list the data events that can be handled by your application:

General Methods	Description
<TableName>_AllowSaveWithErrors	Indicates whether the item should be saved if the item has validation errors. Save will abort by default if the item has validation errors. Runs on the calling tier.
<TableName>_Created	Called after the item is created. Runs on the tier where the item was created.
<TableSetName>_Deleted	Called just after the item has been deleted from the data store. Runs on the server.
<TableSetName>_Deleting	Called just before the item is deleted from the data store. Runs on the server.
<TableSetName>_Inserted	Called just after the item has been inserted into the data store. Runs on the server.
<TableSetName>_Inserting	Called just before the item is inserted into the data store. Runs on the server.
<TableSetName>_Updated	Called just after the item has been updated in the data store. Runs on the server.
<TableSetName>_Updating	Called just before the item is updated in the data store. Runs on the server.
<TableSetName>_Validate	Called when an item is validated on the server.

Access Control Methods	Description
SaveChanges_CanExecute	Called prior to saving changes in the data source to check the permission level of the current user. Runs on the server.
<TableSetName>_CanDelete	Called prior to deleting an item to check permission level of the current user. Runs on the server.
<TableSetName>_CanInsert	Called prior to inserting an item to check the permission level of the current user. Runs on the server.
<TableSetName>_CanRead	Called prior to reading an item to check the permission level of the current user. Runs on the server.
<TableSetName>_CanUpdate	Called prior to updating an item to check the permission level of the current user. Runs on the server.

Query Methods	Description
<TableSetName>_All_ExecuteFailed	Called after the query fails to execute. Runs on the server.
<TableSetName>_All_Executed	Called just after executing the query. This method is not called if the query fails to execute. Runs on the server.
<TableSetName>_All_Executing	Called just before executing the query. Runs on the server.
<TableSetName>_All_PreprocessQuery	Called before the query runs, allowing for additional query customization. Runs on the server.
<TableSetName>_SingleOrDefault_ExecuteFailed	Called after the query fails to execute. Runs on the server.
<TableSetName>_SingleOrDefault_Executed	Called just after executing the query. This method is not called if the query fails to execute. Runs on the server.
<TableSetName>_SingleOrDefault_Executing	Called just before executing the query. Runs on the server.
<TableSetName>_SingleOrDefault_PreprocessQuery	Called before the query runs, allowing for additional query customization. Runs on the server.
<TableSetName>_Single_ExecuteFailed	Called after the query fails to execute. Runs on the server.
<TableSetName>_Single_Executed	Called just after executing the query. This method is not called if the query fails to execute. Runs on the server.
<TableSetName>_Single_Executing	Called just before executing the query. Runs on the server.
<TableSetName>_Single_PreprocessQuery	Called before the query runs, allowing for additional query customization. Runs on the server.

Implicit Query Access Control Methods	Description
<TableSetName>_All_CanExecute	Called prior to executing the query to check the permission level of the current user. Runs on the server.
<TableSetName>_SingleOrDefault_CanExecute	Called prior to executing the query to check permission level of the current user. Runs on the server.
<TableSetName>_Single_CanExecute	Called prior to executing the query to check permission level of the current user. Runs on the server.

Data Source Methods	Description
SaveChanges_ExecuteFailed	Called just after failing to save on the data source. Runs on the server.
SaveChanges_Executed	Called just after successfully saving changes in the data source. Runs on the server.
SaveChanges_Executing	Called just before saving changes in the data source. Runs on the server.

Property Methods
<PropertyName>_Changed	Called just after the property value for an item has changed. Runs on the tier where the property was changed.
<PropertyName>_IsReadOnly	Returns whether the property is read-only. Runs on the tier where the property is accessed.
<PropertyName>_Validate	Called when the property is validated. Runs on the tier where the property is validated.

See Also

Tasks

How to: Handle Screen Events

How to: Handle Query Events

Other Resources

Data: The Information Behind Your Application