Infor LN DLL Customization: Extending Business Logic with Custom Libraries
Infor LN supports DLL-based extensions that enable developers to execute compiled code from within LN 4GL sessions, forms, and business functions. DLL customizations are used when native LN 4GL cannot meet performance requirements, when calling external system APIs, or when implementing complex algorithms that benefit from compiled-language execution. Understanding the DLL integration architecture prevents common pitfalls around memory management, session isolation, and upgrade compatibility.
DLL Architecture in the LN Runtime
LN loads custom DLLs through the bshell runtime environment using the extern.dll function call mechanism. DLLs execute in the same process space as the bshell session, giving them direct access to LN session variables but also creating risk of memory corruption if not carefully managed. The DLL interface supports both stdcall and cdecl calling conventions depending on the target platform.
- Register custom DLLs in the LN environment via $BSE/lib or the designated custom library directory
- Use extern.dll() in 4GL scripts to load and invoke DLL exported functions with typed parameters
- DLLs run in-process with bshell: memory leaks or crashes in DLL code affect the entire LN session
- Support for C/C++ native DLLs and .NET assemblies exposed through COM interop wrappers
- Session isolation: each bshell instance loads its own DLL copy preventing cross-session state contamination
Common DLL Use Cases and Patterns
The most valuable DLL customizations address gaps where LN 4GL is insufficient: calling REST APIs from within LN sessions, executing cryptographic operations for EDI compliance, performing complex mathematical calculations for engineering BOMs, and interfacing with hardware devices on the shop floor. Each pattern requires careful attention to thread safety and error propagation back to the calling 4GL session.
- HTTP client DLLs: invoke external REST APIs from LN sessions for real-time pricing, shipping, or tax calculation
- Cryptographic DLLs: SHA-256 hashing, AES encryption, and digital signature generation for EDI and compliance
- Barcode and label generation: interface with Zebra, SATO, or Honeywell printer SDKs for shop floor label printing
- PDF generation: produce formatted documents using iTextSharp or similar libraries from LN report data
- Hardware integration: connect to scales, scanners, and PLCs through serial or TCP protocols from LN forms
Development, Testing, and Upgrade Safety
Custom DLLs create upgrade risk because Infor may change the bshell runtime, calling conventions, or environment variables between LN versions. Maintaining DLL customizations across LN upgrades requires a documented inventory, version-specific compilation targets, and a regression testing protocol. Store all DLL source code in version control with build scripts that target specific LN platform versions.
- Maintain a DLL inventory document listing each custom library, its purpose, LN sessions that call it, and owner
- Compile DLLs against the same compiler version and platform SDK that matches the target LN runtime
- Implement wrapper 4GL functions that abstract DLL calls so LN sessions are not directly coupled to DLL signatures
- Test all DLLs in a staging environment after every LN service pack and technology update before production
- Log all DLL function calls with input/output parameters for debugging using a shared logging framework
Managing LN DLL customizations? Netray's AI agents audit your custom library inventory and flag upgrade risks automatically.
Related Resources
Infor LN UI Framework Customization Guide
Customize the Infor LN user interface framework with form personalization, scripting, and web client modifications. LN UI development for enhanced user experience.
Infor LNInfor LN API Development Guide
Build integrations with Infor LN APIs using BODs, web services, and the LN Integration Framework. Developer guide for LN REST and SOAP endpoint programming.
Infor LNInfor LN BAAN Backward Compatibility Layer
Navigate BAAN backward compatibility in Infor LN. Legacy 4GL code migration, session mapping, table structure changes, and BaanIV to LN transition strategies.