使用指令是不必要的Visual Studio-随机类

Question

I want to use Random class but I got this error message:

using directive is unnecessary visual studio

---

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Net.Sockets;
using System.Random; //I got this error at this line

namespace Mikrotik
{
....

Answer 1

Quick-fix:

You only need using System; - inside your code you can use Random directly.

Background:

Please read the documentation for C#'s using directive: https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/using-directive

I think you're imagining that using works like how import works in Java where you have to name each type you want to bring into scope or use .* to bring all types into scope. Instead, C#'s using only imports namespaces, making it roughly equivalent to Java's import being used exclusively with the .* syntax.

You're getting the error because there is no namespace System.Random , instead it's a type-name; so you just need using System; - in your code you can use Random as-is.

For pendantry: C#'s using directive has 3 different modes:

1. using namespace; - brings into scope all types in the specified namespace
2. using Alias = namespace.TypeName; - brings into scope a single type, but with an alias. The alias can match the original name.
3. using static namespace.TypeName; - brings only the static members of the specified type into scope.

Not to be confused with C#s using() {} statement, which is completely unrelated to importing types and namespaces.