How to Programmatically Create File-Extension Associations in C ?

Creating File-Extension Associations in C

When a user double-clicks a file associated with a specific application, the operating system launches that application and passes the filename as an argument. This association is established through registry entries.

Registry Configuration

To register a file extension with an application in C , you need to create two registry keys:

1. ProgID: Contains properties such as icon, description, and applications used to open the file.
2. File Extension: Associates the extension with the ProgID, mapping the extension to its file type.

Steps:

1. Create ProgID:

   HKEY_CURRENT_USER\Software\Classes\<ProgID>

2. Associate Extension with ProgID:

   HKEY_CURRENT_USER\Software\Classes\.<Extension>

   Set the value to the ProgID.

Example:

To associate the .blerg extension with the blergcorp.blergapp.v1 file type, create the following registry keys:

HKEY_CURRENT_USER\Software\Classes\blergcorp.blergapp.v1\shell\open\command
@="c:\path\to\app.exe \"%1\""
HKEY_CURRENT_USER\Software\Classes\.blerg
@"blergcorp.blergapp.v1"

Programmatic Approach:

Use the SetValue function in C to set these registry values. If the keys or values don't exist, they will be automatically created.

Considerations:

• Hive Selection: Set keys in HKEY_CURRENT_USERSoftwareClasses for per-user associations, or in HKEY_LOCAL_MACHINESoftwareClasses for system-wide associations.
• Removal of Associations: When an application is uninstalled, its registry entries should be removed to avoid leaving unused entries.

Conclusion:

By creating the appropriate registry entries, you can associate file extensions with your C application, enabling users to open associated files directly through your application.

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