NoSuchCompany.Diagnostics.Guards

The Diagnostics library provides simple and light classes that help checking incoming parameters of a method.

The library is provided as a .netstandard 2.0 DLL so that it can be used in .NET Framework projects (4.6.1) as well as in .NET Core applications. The choice is yours.

Getting Started

1. Install the standard Nuget package into your application.

Package Manager : Install-Package NoSuchCompany.Diagnostics.Guards
CLI : dotnet add package NoSuchCompany.Diagnostics.Guards

2. Well.... use the methods of the Argument static class.

using NoSuchCompany.Diagnostics.Guards;

namespace Application
{
    public class SomeClass
    {
        public SomeClass(string name, Datetime timestampUtc, Socket someSocket)
        {
            Argument.ThrowIfIsEmpty(name, nameof(name));
            Argument.ThrowIfIsNotUtc(timestampUtc, nameof(timestampUtc));
            Argument.ThrowIfIsNull(someSocket, nameof(someSocket));
            
            //  ...            
        }
    }
}

Features

1. Reference types

First, the API provides with a way to prevent null instances from creeping up your application. For example:

public void DoSomething(SomeReferenceType inst)
{
    Argument.ThrowIfIsNull(inst, nameof(inst));   // Stop if inst is bs.
}

2. Guid

We often use Guid as identifiers of entities. We always expect them to represent some entity somewhere in the system. Knowing that we create new entity and assign them a Guid.NewGuid(), empty Guids are not expected and may be a sign of some bug. Hence the following check:

public void DoSomething(Guid entityId)
{
    Argument.ThrowIfIsEmpty(entityId, nameof(entityId));   // Stop if entityId is some bs instance.
}

3. DateTime

A lot of our applications are used by customers across several time zones. As such, our backend does not manipulate DateTime instances that are specified in the local time zone, but only with those specified in the UTC time zone. We let the front-end deal with the time zone. To avoid tricky bugs, we have the following check whenever needed:

public void DoSomething(DateTime timestampUtc)
{
    Argument.ThrowIfIsNotLocal(timestampUtc, nameof(timestampUtc));   // Stop if timestampUtc is not a DateTime expressed in the UTC time zone.
}

The opposite can also be checked:

public void DoSomething(DateTime timestampLocal)
{
    Argument.ThrowIfIsNotUtc(timestampLocal nameof(timestampLocl));   // Stop if timestampLocal is not a DateTime expressed in a local time zone.
}

4. Strings

In some cases, you may require string instances to have some value in it aside from an empty or white-spaced list of characters. Here is the check:

public void NotifyUser(string someImportantMsg)
{
    Argument.ThrowIfIsNullOrWhiteSpace(someImportantMsg nameof(someImportantMsg));   // Stop if we are not notifying anything to the user.
}