UseDLL

Specifies the name of the .dll file to be loaded. If you do not specify an extension, the InstallScript engine assumes that the file has the extension .dll or .exe. Including a path in this parameter is recommended but optional. If the path for the .dll file is not specified in this parameter, the InstallScript engine searches for the .dll file using the same search order that the Windows API function LoadLibrary uses. For more information regarding the search order, see the description of this Windows API function on MSDN.

To include the .dll file in your installation, add it to the appropriate subfolder of the Language Independent folder in the Support Files view. When the installation is running on a target system, the .dll file is available in the temporary directory that is specified by SUPPORTDIR. You can then append the .dll file name to SUPPORTDIR as follows in order to reference the .dll file:

szDLLName = SUPPORTDIR ^ "TheDLL.dll";    UseDLL (szDLLName);

If you do not place your .dll file into your installation (by inserting it into the appropriate folder in the Support Files view), you can instead distribute the file along with the files of your application and then load it from the target system. However, if you do so, you must specify the location to which you install the .dll file so that your installation can reference it. You must also ensure that your installation does not attempt to load the .dll file before it has been transferred to the target system.

Note • The szDLLName parameter does not support uniform resource locators (URLs).

Indicates that the function was unable to load the .dll file into memory.

If UseDLL fails, the most likely cause is that the .dll file was not found. If this happens, make sure that the correct path is specified in the parameter szDLLName.

Another common cause of failure that is associated with using .dll files is related to .dll file dependencies—.dll files that are accessed by the .dll file that you load. If the .dll files that your .dll file must access are not loaded or found, your .dll file call may fail. If this occurs, make sure that the other .dll files are on the system and that they are accessible.

If the script exits or terminates before properly unloading the .dll file with UnUseDLL, the .dll file will be locked in memory. If you attempt to access the .dll file again, your script may fail. You must remove the .dll file from memory by restarting Windows.