Entity Framework Extensions Column PrimaryKey Expression

The ColumnPrimaryKeyExpression allows you to choose a specific property or properties as a key to perform the bulk operations.

The following example uses Login and Password properties as a key to perform BulkMerge.

using (var context = new EntityContext())
{
    context.BulkMerge(list, 
        options => options.ColumnPrimaryKeyExpression = customer => new 
        { 
            customer.Login, 
            customer.Password 
        }
    );
}

Try it online

It will update those records for which the Login and Password already exists in the database and all the new records will be inserted to the database.