Design and Architecture

//Main Form:
private async void toolTrim_Click(object sender, EventArgs e)
{
    var form = new TrimOptions();
    DialogResult result = form.ShowDialog();
    if (result == DialogResult.OK)
    {
        await Task.Run(() => filesList.TrimPages(form.trimFirst, form.trimLast, form.ifBlank));
    }
    form.Dispose();
}

//filesList Class:
public void TrimPages(bool trimFirst, bool trimLast, bool ifBlank)
{
    for (int entry = 0; entry < TotalPDFs; entry++)
    {
        FileEntry thisFile = list[entry];
        thisFile.Trim(trimFirst, trimLast, ifBlank);
    }
}

//thisFile Class:
public void Trim(bool front, bool back, bool ifBlank)
{
    // code
}

//Main Form:
private async void toolTrim_Click(object sender, EventArgs e)
{
    await Task.Run(() => filesList.TrimPages());
}

//filesList Class:
public void TrimPages(bool trimFirst, bool trimLast, bool ifBlank)
{
    var form = new TrimOptions();
    DialogResult result = form.ShowDialog();
    if (result == DialogResult.OK)
	{
		for (int entry = 0; entry < TotalPDFs; entry++)
		{
			PDFEntry thisFile = list[entry];
		}
	}
}

//thisFile Class:
public void Trim(bool front, bool back, bool ifBlank)
{
    // code
}

private void SaveChanges()
{
    foreach (var job in Jobs.Where(x => x.IsDirty).ToList())
    {
        if (job.Id == 0)
        {
            DAL.AddJob(job);
        }
        else
        {
            DAL.UpdateJob(job);
        }
    }

    foreach (var deletedId in deletedJobIds)
    {
        DAL.DeleteJob(deletedId);
    }
}

1. It requires looping over each changed entity and calling either Add or Update. Then I have to call delete.
2. At some point soon I will need to move the BL & DAL to a Web API.

private void SaveChanges()
{
    // Make one call, passing all the data to add/change
    DAL.SaveJobs(Jobs.Where(x => x.IsDirty).ToList(), _deletedJobIs);
}