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Keeping Values in the Registry



The registry is a huge database that holds all necessary the information that the operating system needs to function and communicate with anything that resides in the computer. It is organized as a tree view and functions like Windows Explorer. Although it is highly used by applications installed in the computer, you can use it to store information related to your application and retrieve that information when necessary.

Most of the information in the registration is organized like a dictionary, as a combination of keys and values. In this exercise, we will create an application with a form that the user can move while using the application. When the user closes the application, we will save the location of the form in the registry. The next time the user opens the application, we will retrieve the previous location and apply it to the form.


Practical Learning: Creating the Application

  1. Start Microsoft Visual Studio .NET or Visual C++ .NET and create a Windows Forms Application named Remember1
  2. Right-click the body of the form and click View Code
  3. In the top section of the file, under the other using namespace lines, type
    using namespace Microsoft::Win32;
  4. Return to the form and click its body
  5. In the Properties window, click Events and double-click Closing
  6. Implement the Closing event as follows:
    System::Void Form1_Closing(System::Object *  sender,
    		System::ComponentModel::CancelEventArgs *  e)
    	 // When the user closes the application,
    	 // Examine the HKEY_CURRENT_USER key in the registry
    	 // If there is no key named RememberMe, create it
    	 RegistryKey *regKey = Registry::CurrentUser->CreateSubKey(S"RememberMe");
    	 // In the RememberLocation key, create a sub-key named Left and
    	 // store the Left position of the form in it
    	 regKey->SetValue(S"Left", __box(this->Left));
    	 // Create a sub-key named Top and
    	 // store the Top position of the form in it
    	 regKey->SetValue(S"Top", __box(this->Top));
    	 // Close the registry object
  7. Execute the application
  8. Move the form and close it
  9. Return to the form and double-click its body
  10. Implement the Load event as follows:
    System::Void Form1_Load(System::Object *  sender, System::EventArgs *  e)
    	 // Find out if a key named RememberMe exists in HKEY_CURRENT_USER
    	 // If it exists, open it
    	 RegistryKey *regKey = Registry::CurrentUser->CreateSubKey(S"RememberMe");
    	 // Retrieve the values of its Left and its Top keys
    	 String* L = regKey->GetValue(S"Left")->ToString();
    	 String* T = regKey->GetValue(S"Top")->ToString();
    	 // Set the location of the form based on the values
    	 // retrieved from the registry
    	 this->Left = L->ToInt32(0);
    	 this->Top = T->ToInt32(0);
    	 // Release the resources that the registry variable was using
  11. Execute the application again and notice that it remembers where the form was positioned the last time the application was closed
  12. Open the registry and examine the HKEY_CURRENT_USER node. Notice that it has a new node named RememberMe
  13. Close the registry



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