Get private property of a private property using reflection

Question

public class Foo { private Bar FooBar {get;set;} private class Bar { private string Str {get;set;} public Bar() {Str = "some value";} } }

If I've got something like the above and I have a reference to Foo, how can I use reflection to get the value Str out Foo's FooBar? I know there's no actual reason to ever do something like this (or very very few ways), but I figure there has to be a way to do it and I can't figure out how to accomplish it.

edited because I asked the wrong question in the body that differs from the correct question in the title

What have you tried? A bit of google and some trial and error and you should have this done in no time. — Charles Mager
– Charles Mager, Commented Jun 10, 2015 at 17:26
This really isn't a difficult thing to do, its not all that dissimilar from public ones, you just need to specify different BindingFlags. — Ron Beyer
– Ron Beyer, Commented Jun 10, 2015 at 17:27
My question is different in that every example I've found here only goes one level deep. I typed out the wrong question in the body of the question that differed from the question correctly asked in the title — claudekennilol
– claudekennilol, Commented Jun 10, 2015 at 18:09

Andrew Whitaker · Accepted Answer · 2015-06-10 18:19:12Z

You can use the GetProperty method along with the NonPublic and Instance binding flags.

Assuming you have an instance of Foo, f:

PropertyInfo prop = typeof(Foo).GetProperty("FooBar", BindingFlags.NonPublic | BindingFlags.Instance); MethodInfo getter = prop.GetGetMethod(nonPublic: true); object bar = getter.Invoke(f, null);

Update:

If you want to access the Str property, just do the same thing on the bar object that's retrieved:

PropertyInfo strProperty = bar.GetType().GetProperty("Str", BindingFlags.NonPublic | BindingFlags.Instance); MethodInfo strGetter = strProperty.GetGetMethod(nonPublic: true); string val = (string)strGetter.Invoke(bar, null);

I misspoke in the body of the question and typed out a question different than the one posed in the title. I'm not trying to Foo's FooBar, I'm trying to get Foo's FooBar's Str.
Thanks. I thought I'd tried that but must've had a typo in there somewhere. It really was as easy as it should have been.
If you have an instance of var f = new Foo(), after object bar = getter.Invoke(f, null); bar will still be null and bar.GetType()... will fail with NullReferenceException, correct? Did I missed something?

Arkane · Accepted Answer · 2021-09-07 08:35:38Z

There is a way to slightly simplify Andrew's answer.

Replace the calls to GetGetMethod() + Invoke() with a single call to GetValue() :

PropertyInfo barGetter = typeof(Foo).GetProperty("FooBar", BindingFlags.NonPublic | BindingFlags.Instance); object bar = barGetter.GetValue(f); PropertyInfo strGetter = bar.GetType().GetProperty("Str", BindingFlags.NonPublic | BindingFlags.Instance); string val = (string)strGetter.GetValue(bar);

I did some testing, and I didn't find a difference, then I found this answer, which says that GetValue() calls GetGetMethod() with error checking, so there is no practical difference (unless you worry about performance, but when using Reflection I guess that you won't).

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