FileRegistrationHelper转自【http://www.cnblogs.com/hdl217/archive/2010/11/09/1872983.html】

public class FileRegistrationHelper     {         public static void SetFileAssociation(string extension, string progID)         {             // Create extension subkey             SetValue(Registry.ClassesRoot, extension, progID);              // Create progid subkey             string assemblyFullPath = System.Reflection.Assembly.GetExecutingAssembly().Location.Replace("/", @"\");             StringBuilder sbShellEntry = new StringBuilder();             sbShellEntry.AppendFormat("\"{0}\" \"%1\"", assemblyFullPath);             SetValue(Registry.ClassesRoot, progID + @"\shell\open\command", sbShellEntry.ToString());             StringBuilder sbDefaultIconEntry = new StringBuilder();             sbDefaultIconEntry.AppendFormat("\"{0}\",0", assemblyFullPath);             SetValue(Registry.ClassesRoot, progID + @"\DefaultIcon", sbDefaultIconEntry.ToString());              // Create application subkey             SetValue(Registry.ClassesRoot, @"Applications\" + Path.GetFileName(assemblyFullPath), "", "NoOpenWith");         }          private static void SetValue(RegistryKey root, string subKey, object keyValue)         {             SetValue(root, subKey, keyValue, null);         }         private static void SetValue(RegistryKey root, string subKey, object keyValue, string valueName)         {             bool hasSubKey = ((subKey != null) && (subKey.Length > 0));             RegistryKey key = root;              try             {                 if (hasSubKey) key = root.CreateSubKey(subKey);                 key.SetValue(valueName, keyValue);             }             finally             {                 if (hasSubKey && (key != null)) key.Close();             }         }     }

使用方式：

在app启动时调用方法        public void SetFileAssociation()        {            string extension = ".test";            string title = "something here";            string extensionDescription = "some description";            FileRegistrationHelper.SetFileAssociation(              extension, title + "." + extensionDescription);        }

补充：程序需要管理员权限，方法：

勾选项目属性》安全性》启用clickonce安全性设定，勾选后项目目录Properties下会看见新文件app.manifest，修改该文件：

修改后：

保存后回到项目属性》安全性》启用clickonce安全性设定，取消勾选。

 

事实上注册默认打开方式通常由安装程序执行。