Preconditions.NET

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Introduction

Preconditions.NET provides convenience static methods to help check that a method or a constructor is invoked with proper parameter or not. In other words it checks the pre-conditions. The goal of this class is to improve readability of code.

Preconditions.NET returns the tested value on success, allowing to check and call a method at the same time.

On failure it always throws an ArgumentException, ArgumentNullException or ArgumentOutOfRangeException.

Why Preconditions.NET v2 ?

Preconditions.NET v2.0.0 is a complete rewrite that takes advantage of nullable types, the NotNull attribute and the new .NET 6 CallerArgumentExpression attribute. It is no more mandatory to pass the parameter name being checked.

It also adds new methods (cf. checklist) and remove Check.Zero().

How to use it ?

Because Preconditions.NET is only one code file, you can either copy the Check.cs class or include the NuGet package to your project :

PM> Install-Package Preconditions.NET

Example

public class Employee : Person
{
    public Employee(string name, string id) : base(Check.NotNullOrEmpty(name))
    {
        Id = Check.NullableButNotEmpty(id);
    }

    public string Id { get; }
}

The checklist

• Check.NotNull(object)
• Check.NullableButNotEmpty (string)
• Check.NotNullOrEmpty(string)
• Check.NotNullOrEmpty(IEnumerable)
• Check.HasNoNulls(IEnumerable)
• Check.NotEmpty(Guid)
• Check.FileExists()
• Check.DirectoryExists()
• Check.Positive()
• Check.PositiveOrNull()
• Check.Negative()
• Check.NegativeOrNull()
• Check.NotNegative()
• Check.NotNegativeOrNull()
• Check.True(Func)

Feedback and issues

Feedback, improvements, ideas are welcomed. Feel free to create new issues at the issues section.