C# Select property with name

I am working with MongoDb and at some point, I am needing to create a lambda expression as follows:

...Set(g => g.Profile.First_Name, "Test");

Now, g refers to a class called User, which has a property of type Profile(a different class), with the same name Profile. As you can see, in the lambda expression, I am selecting the First_Name property and then passing the value "Test" to it. My question is, is there a way I can select the property with the property's name itself?

I mean, is something like this possible?

 .... g.Profile. ("First_Name")

As I am typing this, even to me it sounds ridiculous, but I need to dynamically select the particular properties, so I need to select them via their names. How do I actually achieve this?

I tried:

g.Profile.GetType().GetProperty("First_Name")

But it doesn't seem to be equivalent to g.Profile.First_Name. Any ideas on what can be done?