Custom Action Type 17
This custom action calls a dynamic link library (DLL) written in C or C++.
Source
The DLL is installed with the application during the current session. The Source field of the CustomAction table contains a key to the File table. The location of the custom action code is determined by the resolution of the target path for this file; therefore this custom action must be called after that file has been installed and before it is removed.
Type Value
Include the following value in the Type column of the CustomAction table to specify the basic numeric type.
| Constants | Hexadecimal | Decimal |
|---|---|---|
| msidbCustomActionTypeDll + msidbCustomActionTypeSourceFile | 0x011 | 17 |
Target
The DLL is called through the entry point named in the Target field of the CustomAction table, passing a single argument that is the handle to the current install session. The entry point name specified in the table must match that exported from the DLL. Note that if the entry function is not specified by a .DEF file or by a /EXPORT: linker specification, the name may have a leading underscore and a "@4" suffix. The called function must specify the __stdcall calling convention.
Return Processing Options
Include optional flag bits in the Type column of the CustomAction table to specify return processing options. For a description of the options and the values, see Custom Action Return Processing Options.
Execution Scheduling Options
Include optional flag bits in the Type column of the CustomAction table to specify execution scheduling options. These options control the multiple execution of custom actions. For a description of the options, see Custom Action Execution Scheduling Options.
In-Script Execution Options
Include optional flag bits in the Type column of the CustomAction table to specify an in-script execution option. These options copy the action code into the execution, rollback, or commit script. For a description of the options, see Custom Action In-Script Execution Options.
Return Values
See Custom Action Return Values.
Remarks
A custom action that calls a dynamic-link library (DLL) requires a handle to the installation session. If this is also a deferred execution custom action, the session may no longer exist during execution of the installation script. For information on how a custom action of this type can obtain context information, see Obtaining Context Information for Deferred Execution Custom Actions.
Custom actions execute in a separate thread, and may have limited access to the system. Custom actions that run asynchronously block the main thread at the termination of either the current sequence or the install session until they return.
Custom actions that reference an installed file as their source, such as Custom Action Type 17 (DLL), must adhere to the following sequencing restrictions:
- The custom action must be sequenced after the CostFinalize action. This is so that the custom action can resolve the path needed to locate the DLL.
- If the source file is not already installed on the computer, deferred (in-script) custom actions of this type must be sequenced after the InstallFiles action.
- If the source file is not already installed on the computer, non-deferred custom actions of this type must be sequenced after the InstallFinalize action.
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