Top 20 NuGet guard Packages

Simple Guard for .NET http://damienbod.wordpress.com/2014/08/29/policeman-guard-nuget-package/
A really simple C# guard clause/validation library
Useful functionality for .NET applications.
Simple property value checker
A guard implementation that performs asserts/assumptions to prevent invalid code execution.
LiteX.Guard is a simple guard clause argument validation library, that helps you with validation of your arguments. A simple package with guard clause helper methods. This library provides guard clauses that could be used to guard against not expected values. It provides conditions for ...
Guard and Validator library. Example: Guard.That(arg1).IsNotNull().GreaterThan(100); Throws an exception if conditions are not met. Supports the ability to get a list of the failed conditions.
A lightweight and extensible guard clause library. Example: Ensure.Arg(param1, "param1").IsNotNull(); The library is easily extensible through the use of extension methods. Even the main Ensure.Arg(...) call can be overridden to whatever you prefer e.g. Verify.That(...) See the project site for ...
An easy-to-use management system for the ASP.NET Membership system built for ASP.NET MVC 5 applications. This application comes complete with an Area, Controllers, Views and everything you need to start managing your ASP.NET MVC 5 application immediately.
Monads (Maybe, Either, State, Reader, Writer) and monad combinators (Sequence, Sequence_, ReplicateM, ReplicateM_, MapM, MapM_, FoldM, FoldM_, ZipWithM, ZipWithM_, ForM, FilterM, LiftM, LiftM2, LiftM3, LiftM4, LiftM5, Join, When, Unless, Forever, Void, Ap, Compose, Guard, MFilter, MSum) in C#
A small library of helper classes
Argument guard clauses with ReSharper annotations.
Argument guard clauses with ReSharper annotations.
Parameter guard extensions for .NET that checks that a parameter meets the requirements and throws an ArgumentException if it doesn't.
Easy to write, easy to read guard clauses for your .NET methods.
The Diagnostics library provides classes that help checking incoming parameters of a method using the Fluent API or not, depending on what you prefer.
Arguments validation library. Example: Guard.NotNullOrEmpty(bar, "bar");
A simple guard clause project helping you with validation and uniformed exception throwing when validating arguments. This is the source distribution. There is also a portable class library package, Ensure.That, for .Net4+, Silverlight, Windows Phone, WinRT.
'DRY Guard Clauses for c#. Guard_claws provides DRY guard clauses for c# that look like this: Claws.NotNullNotBlank(() => test);
Simple Guard Clause Helper