Entity Framework Extensions Coalesce Destination OnMergeUpdate Expression

Description

The CoalesceDestinationOnMergeUpdateExpression is the inverse of CoalesceOnMergeUpdateExpression, it allows you to update the new value if the database value is null otherwise it keeps the database value when BulkMerge method is executed.

The following example will update only those columns for which the value is null in the database for the specified properties.

using (var context = new EntityContext())
{
    var list = context.Customers.ToList();
    list.ForEach(x => { x.Name += "_Updated"; x.Description += "Add Description"; x.IsActive = false; });
    list.Add(new Customer() { Name ="Customer_C", Description = "Description of C", IsActive = false});
    
    context.BulkMerge(list, options => 
    {
        options.CoalesceDestinationOnMergeUpdateExpression = c => new {c.CustomerID, c.Name, c.Description};
    });                  
}

Try it: EF Core | EF6

• It will update the value in the Description column because the database value is null.
• The value for Name is not null so it will not update the Name column.
• The IsActive will also be updated, because it is not specified in CoalesceDestinationOnMergeUpdateExpression.