Bannerlord Mod Decompiling (ILSpy / ilspycmd)

Setup

dotnet tool install -g ilspycmd

If the user already has the ILSpy GUI app installed, install the matching version (check AppData\Local\Programs\ILSpy\ILSpy.exe's file version) so output is consistent.

Decompiling

Full compilable project (one .cs file per type) — the default for recompiling:

ilspycmd "<dll>" -o "<outdir>" -p

For quick lookups without a full decompile:

ilspycmd "<dll>" -t "Fully.Qualified.TypeName"      # decompile just one type
ilspycmd "<dll>" --dump-table TypeDef | grep -i Foo # RELIABLE type/nested-type existence check
ilspycmd "<dll>" --dump-table TypeRef               # which external assembly a type comes from
ilspycmd "<dll>" --dump-table AssemblyRef           # every assembly + version the DLL references

-l c,i,s,d,e (list classes/interfaces/structs/delegates/enums) is faster to type but gave false negatives in practice — when a -l search comes up empty and you need to be sure a type doesn't exist, confirm with --dump-table TypeDef before concluding anything (e.g. before telling the user an API "doesn't exist in this game version").

Getting a decompiled Bannerlord project to compile again

• Never look for TaleWorlds.* on NuGet — it's the game's own proprietary code, never published there. Reference the BUTR community's Bannerlord.ReferenceAssemblies.Core package instead, pinned to the actual installed game version: Version="<gameVersion>.*-*" (e.g. 1.4.8.*-*). One "Core" package bundles nearly everything a typical mod needs — confirmed to include TaleWorlds.CampaignSystem(.ViewModelCollection), TaleWorlds.MountAndBlade, TaleWorlds.GauntletUI*, TaleWorlds.Core*, TaleWorlds.Library, TaleWorlds.TwoDimension, TaleWorlds.Localization, TaleWorlds.ObjectSystem, etc. It is not split per game module.
• These reference assemblies are compile-time-only stubs (every method body is throw null;) — fine to compile against, useless for reading real logic. To see actual behavior, decompile the real assembly from the game's own bin\Win64_Shipping_Client folder instead.
• dotnet new install Bannerlord.Templates + dotnet new create blmodfx --name X ... scaffolds a known-good reference project fast (Harmony + reference-assemblies wiring already correct) — use the explicit create subcommand; the bare dotnet new blmodfx ... shorthand failed on the .NET 10 SDK. Likewise dotnet new sln on that SDK defaults to a .slnx file, not .sln — dotnet sln x.slnx add <csproj>... still works normally.
• If the mod is split across sibling DLLs (e.g. Foo.dll + Foo.Core.dll), wire a real <ProjectReference> between their two decompiled .csproj files. Don't leave a <Reference><HintPath> pointing at the old original DLL — edits to the sibling project would then be silently ignored on rebuild.
• Nullable/init-accessor polyfill files (System.Diagnostics.CodeAnalysis.*, System.Runtime.CompilerServices.IsExternalInit) sometimes appear as extra loose decompiled .cs files. Delete them before re-adding the Nullable/IsExternalInit NuGet packages for <Nullable>enable</Nullable> support, or you'll get duplicate-type errors.

Fixing invalid C# that ilspycmd emits

ilspycmd's output is not always valid, compilable C# as-is — it has several systematic decompiler artifacts. See ARTIFACTS.md for the checklist and fix pattern for each (ref-casts, _002Ector, protected-member access through a cast, unqualified nested types, and more) before assuming a decompile error is a real bug in the mod.