Calling a base method from a patch is hard

CallingBaseMethodFromPatch.cs

// run this from LINQPad
// don't forget to add the dependencies to Harmony

void Main()
{
	var harmony = new Harmony("test");
	harmony.PatchAll();
	
	var bar = new Bar();
	Prefix(bar);

	// will print
	// Bar.Test(1)
	// Bar.Test(2)
	// Bar.Test(3)
	// Bar.Test(4)
	// Bar.Test(5)
	// Foo.Test(6)
}

[HarmonyPatch(typeof(Foo), "Test")]
class Patch
{
	[HarmonyReversePatch]
	[MethodImpl(MethodImplOptions.NoInlining)]
	public static void Test(Foo instance, string s)
	{
		Console.WriteLine($"Patch.Test({instance}, {s})");
	}
}

static MethodInfo mTest = typeof(Foo).GetMethod("Test");
static FastInvokeHandler Test = MethodInvoker.GetHandler(mTest, true);

delegate void TestDelegate(Foo instance, string s);
static TestDelegate dTest = (TestDelegate)Delegate.CreateDelegate(typeof(TestDelegate), mTest);

public void Prefix(Bar bar)
{
	// normal call
	bar.Test("1");
	
	// casting does not work
	((Foo)bar).Test("2");
	
	// simple invoke does not work
	mTest.Invoke(bar, new[] { "3" });
	
	// FastInvokeHandler does not work
	Test(bar, new[] { "4" });
	
	// delegate does not work
	dTest(bar, "5");
	
	// Reverse patch works
	Patch.Test(bar, "6");
}

public class Foo
{
	public virtual void Test(string s)
	{
		Console.WriteLine($"Foo.Test({s})");
	}
}

public class Bar : Foo
{
	public override void Test(string s)
	{
		Console.WriteLine($"Bar.Test({s})");
	}
}

Would love to see an example where the base method returns a value instead of just being void -- haven't figured out how to get that to work right.

In line 26, you just define your dummy to be the same as the original. If your original has a return value then your dummy would too.

Having a similar issue, but the base class thing i'm trying to access is a protected property. Not sure how to deal with that.

Properties are just methods. You adapt the annotations of the reverse patch according to the documentation to specify a property.