C# Nullable Reference Types

Prevent null reference exceptions with compiler-enforced null safety.

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With Nullable Reference Types enabled, the compiler treats all reference types as non-nullable by default. Types that can be null must be explicitly marked with ? (e.g. string?).

Key Takeaways: C# Nullable Reference Types

Mastering C# Nullable Reference Types helps you write clean and reliable C# code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.

C# Nullable Reference Types Code Example

using System;

class Program {
    static void PrintLength(string? input) {
        if (input != null) {
            Console.WriteLine($"Length: {input.Length}");
        } else {
            Console.WriteLine("Input was null");
        }
    }
    static void Main() {
        PrintLength("Hello C#");
        PrintLength(null);
    }
}

Output

Length: 8
Input was null

Run this example on your own computer. The "Get Started" lesson shows how to set it up.

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C# Nullable Reference Types

💡 Key Takeaways: C# Nullable Reference Types

C# Nullable Reference Types Code Example

Key Takeaways: C# Nullable Reference Types