Question

I’m using WCF Data Services which is working well for most things, but I’m having trouble figuring out how to update an entity that has a related entity collection. For example, in the code below I have a Batch object which has related Departments. In my database this is represented as three tables – Batches, Departments, and Batches_Departments. EF exposes this to me as Batch object with navigation property for Departments.

In the code listed below the Batch object is created and the Departments collection is populated, but when I call SaveChanges, only the Batch object is created in the database. The Departments are ignored. If I set a breakpoint on the SaveChanges line, I can verify the Departments collection is populated.

private void Save()
{
  var batch = new DataService.Batch() { Description = txtDescription.Text, Filename = txtFilename.Text };

  foreach (var department in lstDepartments.CheckedItems)
  {
    var dept = _ctx.Departments
      .Select(d => d)
      .Where(d => d.DepartmentID == ((DataService.Department)department).DepartmentID)
      .First();

    batch.Departments.Add(dept);
  }

  _ctx.AddToBatches(batch);
  _ctx.SaveChanges();
}

I’m sure I’m missing something obvious, but I can’t seem to find it. Any help will be appreciated.

Answer 1

This is a limitation in the current generated code. You will also need to add the following line of code to your program:

context.AddLink(batch, "Departments", dept);

You could also hook into the PropertyChanged event for batch if you prefer.

Edit: I found another option as well. You can do the following rather than AddLink:

private void Save()
{
  var batches = new DataServiceCollection<Batch>(_ctx);
  var batch = new DataService.Batch() { Description = txtDescription.Text, Filename = txtFilename.Text };
  batches.Add(batch);

  foreach (var department in lstDepartments.CheckedItems)
  {
    var dept = _ctx.Departments
      .Select(d => d)
      .Where(d => d.DepartmentID == ((DataService.Department)department).DepartmentID)
      .First();

    batch.Departments.Add(dept);
  }

  // _ctx.AddToBatches(batch);
  _ctx.SaveChanges();
}