ArgDefender 2.1.1

ArgDefender

Fluent argument validation for .NET that keeps guard clauses readable and fast.

Why ArgDefender?

Fail fast: validate inputs at your code boundaries so problems surface immediately, with clear exceptions to pinpoint the offending argument.

• Fluent, chainable guards with clear exception types.
• Most guards tolerate null inputs; add NotNull() when you need to enforce non-null. See null handling for exceptions.
• Automatic parameter names; Guard.Argument(value) captures the name so you do not need to pass strings via nameof().
• Optional secure mode redacts values from selected default messages (see below).

Installation

dotnet add package ArgDefender

Supported frameworks

• .NET 10 (net10.0)

Quick start

using ArgDefender;

public sealed class Person
{
    public Person(string name, int age, Uri homepage)
    {
        Guard.Argument(name).NotNull().NotWhiteSpace();
        Guard.Argument(age).Min(0).Max(130);
        Guard.Argument(homepage).NotNull().UriAbsolute();

        Name = name;
        Age = age;
        Homepage = homepage;
    }

    public string Name { get; }
    public int Age { get; }
    public Uri Homepage { get; }
}

Behavior

ArgDefender throws standard exceptions with consistent, predefined messages:

• Most guards throw ArgumentException and include the parameter name in the message.
• Generic comparison guards (Min, Max, InRange, etc.) throw ArgumentOutOfRangeException. Length, collection-count, and URI-port checks throw ArgumentException.
• Null enforcement (NotNull, NotAllNull) throws ArgumentNullException.

secure: true replaces default messages with "<name> is invalid." for equality, string matching, collection membership, enum flag, and email host checks. For generic comparison guards, it also omits ArgumentOutOfRangeException.ActualValue. It does not redact every guard message or custom message callback.

Examples

Guard chaining

Guard.Argument(name).NotNull().NotEmpty().MaxLength(200);

Custom messages

Guard.Argument(port).InRange(1, 65535, (value, min, max) => $"Port must be {min}-{max}.");

Nullable inputs

string? name = request.Name;
Guard.Argument(name).NotNull().NotWhiteSpace().MaxLength(40);

Secure mode

using ArgDefender;

var apiKey = "demo-invalid-key";
foreach (var secure in new[] { false, true })
{
    try
    {
        Guard.Argument(apiKey, secure: secure).Equal("demo-expected-key");
    }
    catch (ArgumentException exception)
    {
        Console.WriteLine(exception.Message);
    }
}

The default message text is apiKey must be demo-expected-key. without secure mode and apiKey is invalid. with it. The framework appends the parameter name to exception.Message (for example, (Parameter 'apiKey')).

URI checks

var homepage = new Uri("https://example.com");
var redirectUri = new Uri("/callback", UriKind.Relative);
Guard.Argument(homepage).UriHttps();
Guard.Argument(redirectUri).UriRelative();

Enum checks

var status = Status.Pending;
var permissions = Permissions.Read | Permissions.Write;
Guard.Argument(status).EnumDefined();
Guard.Argument(permissions).EnumHasFlag(Permissions.Read);

Defaults and negatives

Guard.Argument(command.Number).NotDefault().NotNegative();

For the detailed list, see docs/standard-validations.md.