Coding Challenge 15

In this tutorial, we are going to learn some topics such as C# extension method ... Have you ever thought about customizing some classes? An extension method enables us to extend a class without damaging or changing the reel codes of the class that we want to modify.

C# Extension Method

To create an extension method, we need to create a static class and one static method. For instance, i would like to customize C# String Class. Let's customize System.String class together and simulate Fluent Validation using C# extension method.

In the code below, you can see one class called FluendValidation and three extension methods.

IsNotNullAndNotEmpty(this string newString) returns true if an email ıs not empty and not null.
IsNotLongEnough returns true ıf the length of a string is greater than 15.
IsStrongEnough returns true if the password contains uppercase, lowercase, numbers, and characters.

FluentValidation.cs

In code block of IsStrongEnough methos, there are patterns such as @”[A-Z]”, @”[a-z]”, @”[0-9]” and @”\W”.

@”[A-Z]” is used to find any character from uppercase A to uppercase Z.
@”[a-z]” is used to find any character from lowercase a to lowercase z.
@”[0-9]” is used to find any character between 0 to 9.
@”\W” is used to find any non-word characters.

public static class FluentValidation
{
    public static bool IsNotNullAndNotEmpty(this string newString)
    {

        return newString is not null && newString != "";
    }

    public static bool IsLongEnough(this string newString)
    {
        return newString.Length > 15 ? true:false;
    }


    public static bool IsStrongEnough(this string newString)
    {
        bool IsStrong = true;
        List<string> patterns= new List<string> { @"[A-Z]", @"[a-z]", @"[0-9]", @"\W" };
        MatchCollection regex;
        patterns.ForEach(pattern =>
        {
            regex = Regex.Matches(newString, pattern);// return a list of all matches
            if (regex.Count==0)
            {
                IsStrong = false;
            }
        }

        );

        return newString.IsLongEnough() && IsStrong ? true : false;

    }
}

Let’s run the Program.cs file and see the results.

Program.cs

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("Hello World!");
        // How to use c# extension method
        string email= "asdfg@hotmail.com";
        string password="1234567gcyh89?AgE-";
        Console.WriteLine(email.IsNotNullAndNotEmpty());
        Console.WriteLine( password.IsNotNullAndNotEmpty());
        Console.WriteLine("IsLongEnough: " + password.IsLongEnough());
        Console.WriteLine("IsStrongEnough: " + password.IsStrongEnough());
    }
}

Output:

asdfg@hotmail.com is not NULL and not EMPTY: True
1234567gcyh89?AgE- is not NULL and not EMPTY: True
IsLongEnough: True
IsStrongEnough: True

As you see in the result, we extended System.String by adding new validation methods.