Entity Framework Core Plus Sync Properties from Database Values

Description

The SyncPropertiesFromDatabaseValues method allows you to synchronize one or more properties from a list using the database value.

Let's explain with the following example:

var products = GetProductToImport();

using (var context = new EntityContext())
{
	context.SyncPropertiesFromDatabaseValues(products, options =>
	{
		options.ColumnPrimaryKeyExpression = x => new { x.Sku };
		options.SyncPropertyExpression = x => new { x.ProductID };
	});
	
	context.BulkMerge(products);
}

In this example, we want to bulk merge (Upsert) a list of products. However, the method GetProductToImport only provides information like the Sku, Name, and Description. The importation currently doesn't know the ProductID as it's coming from an external database.

Since the Sku is unique to a product, we can use it as our key to retrieve the ProductID.

The following line tells the method to use the Sku as the key:

options.ColumnPrimaryKeyExpression = x => new { x.Sku };

And the following line lets the method know which properties it should retrieve from the database:

options.SyncPropertyExpression = x => new { x.ProductID };

After the method is executed, we can now easily use the BulkMerge method, which will use the ProductID that we just retrieved to see if the product already exists or not.

Options

The method currently supports the following options:

Real Life Scenarios

Concurrency

One common use of this method is when you want to quickly solve concurrency issues with the Client Wins scenario to handle concurrency conflicts.

If the concurrency token is currently different from the database, you have to use GetDatabaseValues for every entity only to retrieve the latest concurrency value.

Using SyncPropertiesFromDatabaseValues, you can retrieve all values at once.

Retrieving ID

As shown in the example in the description, when using methods such as BulkUpdate and BulkDelete from Entity Framework Extensions, you do not always have the ID.

While it's possible within Entity Framework Extensions to set a ColumnPrimaryKeyExpression, sometimes it's better to directly use the real key for performance.