Banned APIs

The SDK blocks 50+ dangerous or deprecated APIs at build time, providing suggested alternatives.

Common Banned APIs

Banned	Alternative
`DateTime.Now`	`TimeProvider.System.GetUtcNow()`
`DateTime.UtcNow`	`TimeProvider.System.GetUtcNow()`
`DateTimeOffset.Now`	`TimeProvider.System.GetUtcNow()`
`ArgumentNullException.ThrowIfNull()`	`Throw.IfNull()`
`ArgumentException.ThrowIfNullOrEmpty()`	`Throw.IfNullOrEmpty()`
`StringComparison.InvariantCulture`	`StringComparison.Ordinal`
`StringComparison.InvariantCultureIgnoreCase`	`StringComparison.OrdinalIgnoreCase`
`file.CreationTime`	`file.CreationTimeUtc`
`file.LastAccessTime`	`file.LastAccessTimeUtc`
`file.LastWriteTime`	`file.LastWriteTimeUtc`

Why These Are Banned

DateTime.Now / DateTime.UtcNow

Direct time access is:

Untestable - Can't mock time in unit tests
Inconsistent - Different results on different machines

Use TimeProvider instead:

// Inject TimeProvider
public class MyService(TimeProvider time)
{
    public void Process()
    {
        var now = time.GetUtcNow();
    }
}

// In tests
var fakeTime = new FakeTimeProvider();
var service = new MyService(fakeTime);
fakeTime.Advance(TimeSpan.FromHours(1));

ArgumentNullException.ThrowIfNull

The SDK provides Throw.IfNull with better diagnostics:

// SDK-provided guard
Throw.IfNull(argument);           // CallerArgumentExpression included
Throw.IfNullOrEmpty(str);         // String-specific
Throw.IfNullOrWhiteSpace(str);    // Whitespace check

InvariantCulture

InvariantCulture is rarely what you want:

For machine-readable data: Use Ordinal
For user-facing data: Use CurrentCulture

Suppressing Banned APIs

For legitimate use cases, suppress with a comment:

#pragma warning disable RS0030 // Banned API
var legacy = DateTime.Now; // Required for legacy compatibility
#pragma warning restore RS0030

Or in .editorconfig:

[**/LegacyCode/**/*.cs]
dotnet_diagnostic.RS0030.severity = none