Search through all methods that exist in all assemblies and run a test on their method bodies

SearchThroughAllMethodBodies.cs

using HarmonyLib;
using MonoMod.Utils;
using System;
using System.Linq;
using System.Reflection;

class Program
{
	static void Main()
	{
		// prepare search term outside the loop for efficiency
		var operandSearchTerm = AccessTools.Constructor(typeof(ArgumentNullException));

		// create a ILGenerator from scratch (required by PatchProcessor.GetOriginalInstructions)
		var dummyMethod = new DynamicMethodDefinition("Dummy", typeof(void), Array.Empty<Type>());
		var generator = dummyMethod.GetILGenerator();

		// use current appdomain to get all types and all methods and their instructions
		// this code excludes any generics because you cannot get a method body without
		// specifying the concrete types and we don't know which ones we would use
		AppDomain.CurrentDomain.GetAssemblies()
			.SelectMany(assembly => assembly.GetTypes())
			.Where(type => type.IsGenericType == false)
			.SelectMany(type =>
			{
				var methods = AccessTools.GetDeclaredMethods(type).Cast<MethodBase>();
				var constructors = AccessTools.GetDeclaredConstructors(type).Cast<MethodBase>();
				return methods.Union(constructors);
			})
			.Where(member => member.IsGenericMethod == false && member.GetMethodBody() != null)
			.Do(member =>
			{
				var instructions = PatchProcessor.GetOriginalInstructions(member, generator);

				// here, we can apply any logic necessary - replace with your own logic
				if (instructions.Any(instructions => instructions.OperandIs(operandSearchTerm)))
					Console.WriteLine($"=> {member.DeclaringType.Name}::{member.Name}");
			});
	}

	// for .NET Core 3.1 it should output something like:
	// => ArgIterator::GetNextArg
	// => RuntimeType::SanityCheckGenericArguments
	// => RuntimeType::GetPropertyImpl
	// => RuntimeType::GetEvent
	// => RuntimeType::GetField
	// => RuntimeType::GetInterface
	// => RuntimeType::GetNestedType
	// => RuntimeType::GetMember
	// => RuntimeType::MakeGenericType
	// => Type::GetTypeArray
	// => TaskToApm::End
	// => HStringMarshaler::ConvertToNative
	// => HStringMarshaler::ConvertToNativeReference
	// => RuntimeMethodInfo::MakeGenericMethod
	// => TaskToApm::End
	// => MetadataBuilder::LookupToken
	// => SignatureWriter::WriteTypeSignature
	// => SignatureWriter::WritePrimitiveValue
	// => GenericParameter::.ctor
	// => EmbeddedPortablePdbReader::.ctor
}