# FIX5 - binary compatibility for existing 10.0.0-3 clients

This revision is specifically for drop-in replacement scenarios where existing applications **must not be recompiled**.

Key correction: the legacy method is `IMSApiDotNetBase.setProperty(System.String,System.String)` with a static call signature. FIX4 had accidentally changed it to an instance/virtual method, which produces `System.MissingMethodException` in already compiled clients.

The correction is in the shared source, therefore it applies equally to the `net48` and `netstandard2.0` outputs.

Use `scripts\check-legacy-binary-compat.ps1` after building. It compiles its smoke EXE against the untouched original 10.0.0-3 DLL, then runs the unchanged EXE separately with each new target DLL.