C# using static usage

Question

see the code first
using System;
using static System.Math; // static directive
using static System.String;
namespace CSharpFeatures
{
class StaticImport
{
public static void Main(string[] args)
{
double sqrt = Sqrt(144); // Calling without class name
string newStr = Concat("javatpoint",".com");
Console.WriteLine(sqrt);
Console.WriteLine(newStr);
}
}
}

i understand that if i write using static System.String; then i do not have to write String before Concat function i guess it is good for static class. when we call static class function then we do not have to create instance rather we write static class name dot function name.

but using static may not be useful when i have to create instance of class before calling the function. am i right ?

am i right using static has utility only for static class ? please guide me. Thanks

Answer 1

When using using static you now need to know properties and methods without preceding with the namespace/class. It's okay if you know the properties and methods e.g.

Example 1, a method coded as static,

using System.Text.RegularExpressions;

namespace IncrementSequenceConsole.Classes
{
    public class Helpers
    {
        public static string NextValue(string sender)
        {
            string value = Regex.Match(sender, "[0-9]+$").Value;
            return sender[..^value.Length] + (long.Parse(value) + 1)
                .ToString().PadLeft(value.Length, '0');
        }
    }
}

Usage

using System;
using System.Runtime.CompilerServices;
using IncrementSequenceConsole.Classes;

namespace IncrementSequenceConsole
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine($"          F1124   {Helpers.NextValue("F1124")}");
            Console.WriteLine($"       1278-120   {Helpers.NextValue("1278-120")}");
            Console.WriteLine($"           F102   {Helpers.NextValue("F102")}");
            Console.WriteLine($"3999/IKL/VII/21   {Helpers.NextValue("3999/IKL/VII/21")}");
            Console.ReadLine();
        }

    }
}

Example 2 with static

using System;
using System.Runtime.CompilerServices;
using static IncrementSequenceConsole.Classes.Helpers;

namespace IncrementSequenceConsole
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine($"          F1124   {NextValue("F1124")}");
            Console.WriteLine($"       1278-120   {NextValue("1278-120")}");
            Console.WriteLine($"           F102   {NextValue("F102")}");
            Console.WriteLine($"3999/IKL/VII/21   {NextValue("3999/IKL/VII/21")}");
            Console.ReadLine();
        }

    }
}

If I add additional methods or properties I know them unlike say Math where I may not know all methods thus making it more difficult to find them.

With that I'd go with an alias.

using System;
using System.Runtime.CompilerServices;
using H = IncrementSequenceConsole.Classes.Helpers;

namespace IncrementSequenceConsole
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine($"          F1124   {H.NextValue("F1124")}");
            Console.WriteLine($"       1278-120   {H.NextValue("1278-120")}");
            Console.WriteLine($"           F102   {H.NextValue("F102")}");
            Console.WriteLine($"3999/IKL/VII/21   {H.NextValue("3999/IKL/VII/21")}");
            Console.ReadLine();
        }

    }
}

My style of coding it's extremely rare to have a reason to instantiate an instance of a class of my own but when doing so side with aliasing.

Answer 2

I often use it to simplify code, like in the sample with PI and Pow from MSDN doc : static-modifier
(in fact, it is VS which suggests the modification when I call some functions from other Namespaces...)