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A simple package with guard clause extensions.

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Guard Clauses

A simple extensible package with guard clause extensions.

A guard clause is a software pattern that simplifies complex functions by "failing fast", checking for invalid inputs up front and immediately failing if any are found.

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public void ProcessOrder(Order order)
    Guard.Against.Null(order, nameof(order));

// process order here


// OR

public class Order { private string _name; private int _quantity; private long _max; private decimal _unitPrice; private DateTime _dateCreated;

public Order(string name, int quantity, long max, decimal unitPrice, DateTime dateCreated)
    _name = Guard.Against.NullOrWhiteSpace(name, nameof(name));
    _quantity = Guard.Against.NegativeOrZero(quantity, nameof(quantity));
    _max = Guard.Against.Zero(max, nameof(max));
    _unitPrice = Guard.Against.Negative(unitPrice, nameof(unitPrice));
    _dateCreated = Guard.Against.OutOfSQLDateRange(dateCreated, nameof(dateCreated));


Supported Guard Clauses

  • Guard.Against.Null (throws if input is null)
  • Guard.Against.NullOrEmpty (throws if string, guid or array input is null or empty)
  • Guard.Against.NullOrWhiteSpace (throws if string input is null, empty or whitespace)
  • Guard.Against.OutOfRange (throws if integer/DateTime/enum input is outside a provided range)
  • Guard.Against.OutOfSQLDateRange (throws if DateTime input is outside the valid range of SQL Server DateTime values)
  • Guard.Against.Zero (throws if number input is zero)

Extending with your own Guard Clauses

To extend your own guards, you can do the following:

// Using the same namespace will make sure your code picks up your 
// extensions no matter where they are in your codebase.
namespace Ardalis.GuardClauses
    public static class FooGuard
        public static void Foo(this IGuardClause guardClause, string input, string parameterName)
            if (input?.ToLower() == "foo")
                throw new ArgumentException("Should not have been foo!", parameterName);

// Usage public void SomeMethod(string something) { Guard.Against.Foo(something, nameof(something)); }


Build Notes (for maintainers)

  • Remember to update the PackageVersion in the csproj file and then a build on master should automatically publish the new package to
  • Add a release with form
    to GitHub Releases in order for the package to actually be published to Nuget. Otherwise it will claim to have been successful but is lying to you.

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