using System;
using System.Management;             //需要引用System.Management

public class Sample
{
     public static void Main(string[] args)
     {
         string PrinterName = "Adobe PDF";
         ManagementObjectSearcher query;
         ManagementObjectCollection queryCollection;
         string _classname = "SELECT * FROM Win32_Printer";

         query = new ManagementObjectSearcher(_classname);
         queryCollection = query.Get();

         foreach (ManagementObject mo in queryCollection)
         {
             if (string.Compare(mo["Name"].ToString(), PrinterName, true) == 0)
             {
                 mo.InvokeMethod("SetDefaultPrinter", null);
                 break;
             }
         }

         foreach (ManagementObject mo in queryCollection)
         {
                 Console.WriteLine(mo["Name"].ToString());
         }

        Console.ReadLine();
     }
}