.NET library to access any running Excel Application (single or multiple instances). Based on CodeProject | Automate multiple Excel instances
All running Excel instances are reliably returned, even workbooks opened from OneDrive. It extends the Excel type hierarchy by adding a top-level Session that contains Applications that contains Workbooks that contains Sheets etc.
Applications is the main access point. It returns an untyped sequence because Excel.Application is an embedded interop type. Elements can be safely cast to Excel.Application by the consuming project via the main Session class.
[TestMethod]
public void Session_TracksNewWorkbook_Success()
{
// Arrange
// Count existing Excel instances if any are open.
Session session = Session.Current;
int countStart = session.Applications.OfType<Excel.Application>().Count();
int countUpdate;
// Act
// Open a new Excel instance and record.
Excel.Application? app = null;
try
{
app = new();
app.Visible = true;
Excel.Workbook wb = app.Workbooks.Add(app.Workbooks.Count + 1);
countUpdate = session.Applications.OfType<Excel.Application>().Count();
wb.Close();
}
finally
{
app?.Quit();
}
// Assert
// Check that Session succesfully tracked the new Excel instance.
// Check that the starting state is returned.
Assert.IsTrue(countUpdate > countStart);
Assert.IsTrue(countStart == session.Applications.OfType<Excel.Application>().Count());
}Some extras, possibly useful, are also included. Extension methods for Appication and Process conversion.