C# Passing / retrieving a property name from a parameter without reflection

Question

I want to pass a property to a function such that the function knows both the value of the property and the name of the property. This is so I can return errors that match the property names.

I currently have code like this:

var userNameField = personField.GetChildField(f => f.UserName, nameof(personField.Value.UserName));

many times repeated, so the 2nd parameter is the name of the property inside the lambda of the 1st parameter.

Is it possible to automate this parameter so:

1. The duplicate code is gone
2. The string name of the property is calculated at compile-time, not run-time for every call

Ideally I would like my code to simply look like:

var userNameField = personField.GetChildField(f => f.UserName);

I have got this working using reflection using Expression<Func... ie ((MemberExpression) getPropertyFunc.Body).Member.Name; but this is too slow, in particular compiling the expression into a function which I can use to fetch the property value.

Similarly, I have read through the ideas here: Get name of property as a string

Is there any way of populating the property name from the GetChildField function at compile time? Or encoding it into the model somehow?

Answer 1

It is possible by following:

Item model=new Item();    
var propertyInfo = model.GetType();    
var value=propertyInfo.GetProperty("IrrA").GetValue(model, null).ToString();

Answer 2

According to the Roslyn documentation found here the nameof operator is evaluated at compile-time per the first line under the "Semantics" section that reads

The nameof expression is a constant. In all cases, nameof(...) is evaluated at compile-time to produce a string. Its argument is not evaluated at runtime, and is considered unreachable code (however it does not emit an "unreachable code" warning).