Prevent null references

Use defensive coding practices to prevent null reference exceptions by properly handling potentially null values throughout your code.

1. Properly initialize objects instead of using default values when instantiation is needed: ```csharp // AVOID: Using default without initialization ArrayBuilder processes = default; // Could cause NullReferenceException when adding items

// PREFER: Proper instantiation ArrayBuilder processes = new ArrayBuilder();

2. **Capture and check results** of methods that might return null before using them:
```csharp
// AVOID: Potential NullReferenceException if ReadLine() returns null
while (!remoteHandle.Process.StandardOutput.ReadLine().EndsWith(message))
{
    Thread.Sleep(20);
}

// PREFER: Capture and check for null
string? line;
while ((line = remoteHandle.Process.StandardOutput.ReadLine()) != null && 
       !line.EndsWith(message))
{
    Thread.Sleep(20);
}

1. Map null values to appropriate empty structures to maintain consistent behavior: ```csharp // AVOID: Will throw if context is null return SignData(new ReadOnlySpan(data), destination.AsSpan(), new ReadOnlySpan(context));

// PREFER: Properly handle null context return SignData(new ReadOnlySpan(data), destination.AsSpan(), context == null ? ReadOnlySpan.Empty : new ReadOnlySpan(context));

4. **Use pattern matching** for more readable and concise null checks:
```csharp
// AVOID: Traditional null check with equality operator
if (setMethod == null || !setMethod.IsPublic)

// PREFER: Modern pattern matching
if (setMethod is null || !setMethod.IsPublic)

1. Combine conditions using pattern matching for cleaner code: ```csharp // AVOID: Multiple conditions checked separately if (changeToken is not null && changeToken is not NullChangeToken)

// PREFER: Combine related checks if (changeToken is not (null or NullChangeToken)) ```

When adding validation in public APIs, favor the built-in helpers like ArgumentNullException.ThrowIfNull() over custom throw helpers for better readability and standardization.