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Catalog

Console class

C# Input and output

C# Output to console

C# Read... From the console

int.Parse() Convert integer type method

The sample program

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Console class

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C# Input and output

         Let's talk about C# Input and output of ：

Console.WriteLine("Hello,World!");
Console.ReadLine();

         Remember Java The output statement of I'm already familiar with it ：

System.out.print();
System.out.printf();
System.out.println();

         Similar structures Console yes C# Console class in
         utilize Console Class can be very convenient for console Input / Output

         There are two common output methods ：

Console.WriteLine();    /*  Console . Write a line (); */
Console.Write();    /*  Console . Write (); */

         You can see that ？
         The only difference is to add Line After the output, the line will wrap ！

         What about the input method ：

Console.Read();
Console.ReadLine();

    Read a line This method returns string type

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C# Output to console

         We have three ways to output to the console ：

Console.WriteLine();
Console.WriteLine( The value to output );
Console.WriteLine(" Format string ",  Variable list );

         The first two are related to Java Medium

System.out.println();

         The usage is the same Just try it yourself

         The third way Is the most popular one ！ Place holder

        In this way C、Java、C# Chinese are very popular ！

         for instance ：

string course = "C#";
Console.WriteLine(" I'm learning  >>> {0}", course);

     When you run, it will output ：

 I'm learning  >>> C#

         In this form WriteLine() The parameter of consists of two parts ：

(" Format string ", Variable list )

         Format string by ：

" I'm learning  >>> {0}"

         and

{0}

         be called Place holder What position does it occupy ？ Occupy is the back

course

         The position of the variable

         We are Format string In turn use

{0}
{1}
{2}
{N}

         Represents the variable to be output Then arrange the variables in the variable list in turn
        {0} Corresponding to the first variable {1} Corresponding to the next second variable And so on

         This way is much more convenient than using a plus sign ：

Console.WriteLine(name + ", " + course + ", " + age);
Console.WriteLine("{0}, {1}, {2}", name, course, age);

         Because when you connect with a plus sign Easy to make mistakes and troublesome
        Placeholder mode is easy to maintain ！

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C# Read... From the console

         And output Console.WriteLine() Corresponding Input can be used Console.ReadLine() Method
        Write It means to write Read It means reading

        Console.ReadLine() Returns a string We can assign it directly to a string variable ！

        code：

string name = Console.ReadLine();

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int.Parse() Convert integer type method

         There's another magical use ！ That is to say If we want to input and save plastic data What should I do ？
         It's simple Convert the returned string into an integer ！

        code:

int age = int.Parse(Console.ReadLine());

         Remember the concept of data conversion ？ int.Parse() Is the method of converting strings to integers

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The sample program

         Write a small project to get familiar with Console input and output user information

        VSCode code：

using System;

namespace _2. Place holder _ Console read in assignment conversion _ Output user information 
{
    class Program
    {
        static void Main(string[] args)
        {
            /*   demonstration 
             * 
             *  Console I / O 
             *  Place holder 
             *  Console read 
             *  Console read in assignment conversion 
             */

            /*  Program preparation  */
            Console.Write(" Please enter a user name  <<< ");
            string name = Console.ReadLine();    //  The program executes here and waits for the user to input the string assigned to  name  Variable 
            Console.Write(" Please enter the user level  <<< ");
            int level = int.Parse(Console.ReadLine());    //  Program execution to the number of input string   It has to be numbers   Then it is transformed into shaping data and assigned to  level

            /*  Program output  */
            Console.WriteLine();
            Console.WriteLine("##################################################");
            Console.WriteLine(name + "  Hello ！ Your rank is  " + level);    //  Plus sign connection output 
            Console.WriteLine("{0}  Hello ！ Your rank is  {1}", name, level);    //  Placeholder output 

            /*  Program end  */
            Console.ReadLine();
        }
    }
}

        VSCode demo：

Windows PowerShell
 copyright  (C) 2014 Microsoft Corporation. All rights reserved .

PS E:\C#> cd "e:\C#\" ; if ($?) { dotnet run Program.cs }
E:\C#\Program.cs(19,27): warning CS8600:  take  null  Text or possible  null  The value is converted to a value that cannot be  null  type . [E:\C#\C#.csproj]
E:\C#\Program.cs(21,35): warning CS8604: “int int.Parse(string s)” Parameter in “s” It's possible that  null  Reference arguments . [E:\C#\C#.csproj]
 Please enter a user name  <<<  Li erha 
 Please enter the user level  <<< 1314

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 Li erha   Hello ！ Your rank is  1314
 Li erha   Hello ！ Your rank is  1314

PS E:\C#>

        Although there is a warning message at compile time But it does not affect the operation of the program