Deleting Data

To remove an entity from the database we can do the following:

var authorToDelete = _context.Authors.Find(1);
if (authorToDelete != null)
{
  _context.Authors.Remove(authorToDelete);
  _context.SaveChanges();
}

Efficient deleting with ExecuteDelete

Let's assume that you need to delete all Blogs with a rating below a certain threshold. The traditional SaveChanges() approach requires you to do the following:

foreach (var blog in context.Blogs.Where(b => b.Rating < 3))
{
    context.Blogs.Remove(blog);
}

context.SaveChanges();

This is quite an inefficient way to perform this task: we query the database for all Blogs matching our filter, and then we query, materialize and track all those instances; the number of matching entities could be huge. We then tell EF's change tracker that each Blog needs to be removed, and apply those changes by calling SaveChanges(), which generates a DELETE statement for each and every one of them.

Here is the same task performed via the ExecuteDelete API:

context.Blogs.Where(b => b.Rating < 3).ExecuteDelete();

This uses the familiar LINQ operators to determine which Blogs should be affected - just as if we were querying them - and then tells EF to execute a SQL DELETE against the database:

DELETE FROM [b]
FROM [Blogs] AS [b]
WHERE [b].[Rating] < 3

Aside from being simpler and shorter, this executes very efficiently in the database, without loading any data from the database or involving EF's change tracker. Note that you can use arbitrary LINQ operators to select which Blogs you'd like to delete - these are translated to SQL for execution at the database, just as if you were querying those Blogs out.