C＃从registry中获取SystemRestore的状态

我试图从C＃中的子项“HKLM \ SOFTWARE \微软\的Windows NT \ CurrentVersion \ SystemRestore”读取registry项“RPSessionInterval”。 我正在使用下面的代码并得到exception“对象引用未设置为对象的实例”。

string systemRestore = @"SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRestore"; RegistryKey baseRegistryKey = Registry.LocalMachine; public string SystemRestoreStatus(string subKey, string keyName) { RegistryKey rkSubKey = baseRegistryKey.OpenSubKey(systemRestore); if (rkSubKey != null) { try { string sysRestore = rkSubKey.GetValue("RPSessionInterval").ToString(); if (string.Compare(sysRestore, "1") == 0) { MessageBox.Show("System Restore is Enabled!"); return "System Restore is Enabled!"; } else if (string.Compare(sysRestore, "0") == 0) { MessageBox.Show("System Restore is Disabled!"); return "System Restore is Disabled!"; } else { return null; } } catch (Exception ex) //This exception is thrown { MessageBox.Show("Error while reading registry key: " + subKey + "\\" + keyName + ". ErrorMessage: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); return null; } } else { MessageBox.Show("Error while reading registry key: " + subKey + "\\" + keyName + " does not exist!", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); return null; } } 

这是一张图片，显示registry项实际存在：

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 string sysRestore = rkSubKey.GetValue(keyName).ToString(); 

 string sysRestore = rkSubKey.GetValue(keyName) as string; 

 SOFTWARE\Wow6432Node\Microsoft\...