dnlib

Enhanced strong naming allows for more complex signing scenarios. You can perform this without key migration or with key migration.

Without key migration: Requires a StrongNameKey and a StrongNamePublicKey. With key migration: Requires a StrongNameKey and StrongNamePublicKey for both the signature and the identity, plus an identityKey and identityPubKey.

To sign an assembly with a strong name, use ModuleWriterOptions.InitializeStrongNameSigning. This requires a ModuleDef and a StrongNameKey (pointing to your .snk file).

using dnlib.DotNet.Writer;

ModuleDef mod = ModuleDefMD.Load(...);
var opts = new ModuleWriterOptions(mod);
var signatureKey = new StrongNameKey(@"c:\my\file.snk");

// Initializes required properties for signing
opts.InitializeStrongNameSigning(mod, signatureKey);

mod.Write(@"C:\out\file.dll", opts);

Use ModuleDefMD.Load() to open a .NET module. It is highly recommended to create a ModuleContext using ModuleDef.CreateModuleContext() and pass it to the Load method to manage assembly and type resolution.

If you are working with obfuscated Unity/Mono assemblies, you must create a ModuleCreationOptions instance, set ModuleCreationOptions.Runtime to CLRRuntimeKind.Mono, and pass it to the Load method.

Note: If you are working with .NET Core assemblies, you may need to disable GAC loading and manually add .NET Core reference assembly search paths to your resolver.

By default, dnlib reads PDB files from disk. To save a PDB file along with your assembly, use ModuleWriterOptions (or NativeModuleWriterOptions) and set the WritePdb property to true.

You can specify a custom filename via PdbFileName or provide a custom stream via PdbStream. If using PdbStream, you must also initialize PdbFileName so the name is correctly written into the PE file.

ModuleContext modCtx = ModuleDef.CreateModuleContext();
var mod = ModuleDefMD.Load(@"C:\myfile.dll", modCtx);

var wopts = new dnlib.DotNet.Writer.ModuleWriterOptions(mod);
wopts.WritePdb = true;
// wopts.PdbFileName = @"C:\out2.pdb"; // Optional: set custom filename

mod.Write(@"C:\out.dll", wopts);

Use module.Write() to save an assembly to a file or a Stream.

For C++/CLI assemblies (which contain native code), use module.NativeWrite() instead. You can detect if an assembly contains native code at runtime by checking the IsILOnly property.

// Standard IL assembly
module.Write(@"C:\saved-assembly.dll");

// C++/CLI or native-containing assembly
if (module.IsILOnly) {
    module.Write(@"C:\saved-assembly.dll");
} else {
    module.NativeWrite(@"C:\saved-assembly.dll");
}

To resolve TypeRef or MemberRef objects, use their .Resolve() methods. These rely on the module.Context.Resolver.

It is critical to share a single ModuleContext across all modules you open to ensure consistent resolution. You should also add any modules you open to the AssemblyResolver cache to speed up subsequent lookups.

To use standard .NET types (like System.Console) within a module you are building, use the Importer class. This creates a TypeRef, MemberRef, or FieldRef in your module that points to the original assembly, rather than duplicating the actual definition.

ITypeDefOrRef consoleRef = importer.Import(typeof(System.Console));
IMethod writeLine = importer.Import(typeof(System.Console).GetMethod("WriteLine"));