Hiring the right C# developer can be the key to your project's success. However, identifying a skilled and competent candidate from a pool of applicants can be a daunting task. This undertaking is comparable to disentangling the complex array of metaphysical theories to understand the nature of reality. Below are seven pertinent points of inquiry that can guide you in this labyrinthine journey.

• What is your proficiency in C# and .NET frameworks?

This query is paramount because C# (C Sharp) operates within the .NET framework. Hence, it is crucial for a developer to be well-acquainted with both. Similar to how a mathematical theorem requires solid foundational axioms, a C# developer needs to have a robust understanding of .NET in addition to C#.

• Can you provide evidence of projects you have completed using C#?

This question is analogous to requiring supporting empirical evidence in scientific research. It allows you to assess the candidate's practical experience and their ability to apply their theoretical knowledge. The complexity and the size of the projects they have worked on can provide insights into the developer's hands-on experience and problem-solving skills.

• How do you manage memory in C#?

Memory management is a critical aspect of any programming language. It is akin to economic resource allocation where optimal utilization leads to greater efficiency. A proficient C# developer should be adept at employing Garbage Collection and understanding the nuances of ‘Dispose’ and ‘Finalize’ methods in C#.

• Can you demonstrate your understanding of Multithreading in C#?

Multithreading, in C#, allows for concurrent execution of two or more parts of a program for maximum utilization of the CPU. It's the computational equivalent of Newton's law of motion — each thread, like an object, continues in its state of rest or uniform motion unless compelled to change that state. A developer should be able to describe how to implement and manage multithreading in C#.

• What are the principles of Object-Oriented Programming (OOP) and how does C# embody them?

OOP is a programming paradigm that uses "objects" to design applications and software. The four principles of OOP are Encapsulation, Abstraction, Inheritance, and Polymorphism. A C# developer, akin to a chess grandmaster, should be able to execute these strategies effectively, considering each as a strategic move towards ensuring a successful application design.

• How do you approach debugging a C# application?

Like a seasoned detective combing through a crime scene for evidence, a C# developer must possess the ability to trace, diagnose, and rectify code errors. Be it utilizing breakpoints or tracing through log files, an expert developer should be able to handle exceptions and recover gracefully from failures.

• What measures do you employ to secure a C# application?

In an era where cyber threats resemble a modern permutation of Machiavellian tactics, ensuring application security is more critical than ever. From data encryption to user authentication, a developer should be well-versed in strategies to protect applications from potential threats.

Asking these seven questions can aid in discerning the skills and competencies of a C# developer. This process is akin to conducting a thorough mathematical proof — each question, each step, contributes to validating the potential candidate's capabilities.

Remember, as with any historical artifact, where even the smallest inscriptions can offer profound insights into a civilization, the responses to these questions hold the key to discerning the inherent quality and potential of your C# developer candidate.