I want to aquire all items in the folder that starts later than a specified
time. How can I use the Restrict method to achieve this?

In MSDN, there is a VB example:

sFilter = "[LastModificationTime] > '" & Format("1/15/99 3:30pm", "ddddd
h:nn AMPM") & "'"

But how about C#?
I tried using String.Format with the following code but failed:

           Outlook.Items appointmentItems;
           try
           {
               string strStartTime = String.Format(startTime.ToString(),
"ddddd h:nn AMPM");
               appointmentItems = folder.Items.Restrict("[MessageClass] =
'IPM.Appointment'");
               appointmentItems = folder.Items.Restrict("[Start] >= '" +
strStartTime + "'"); //Exception occurred here
           }
           catch(Exception ex)
           {
               ......
           }