Outlook Interop c# sort items not working

问题:

I have stumbled upon a problem where the Outlook items table sort method does not give desired results - despite the ascending or descending the method GetLast() always returns the same email item. Code as follows:

Application olApp = new Application();
NameSpace olNS = olApp.GetNamespace("MAPI");
MAPIFolder oFolder = olNS.GetDefaultFolder(OlDefaultFolders.olFolderInbox);

Explorer oExp = oFolder.GetExplorer(false);
//olNS.Logon( false, true);

result = new IOActionResult(null);

oFolder.Items.Sort("[ReceivedTime]");

var subject = oFolder.Items.GetLast().Subject;

I have tried specifying following:

oFolder.Items.Sort("[ReceivedTime]", true);
oFolder.Items.Sort("[ReceivedTime]", false);
oFolder.Items.Sort("[ReceivedTime]", OlSortOrder.olAscending);
oFolder.Items.Sort("[ReceivedTime]", OlSortOrder.olDescending);

Which did not seem to work either... Any thoughts appreciated!

回答1:

On your last line;

var subject = oFolder.Items.GetLast().Subject;

You are being returned a new Items object from Outlook, so your sort was actually performed on an instance that you no longer have a reference to.

Change your code to look like this;

Application  olApp = new Application();
NameSpace olNS = olApp.GetNamespace("MAPI");
MAPIFolder oFolder = olNS.GetDefaultFolder(OlDefaultFolders.olFolderInbox);

Items items = oFolder.Items;
items.Sort("[ReceivedTime]");

var subject = items.GetLast().Subject;

A good rule of thumb when developing against Outlook is to always assign intermediary members of objects to their own local variable. This is particular relevant for releasing them later on.