Skip to main content
Engineering LibreTexts

7.7: C# Examples

  • Page ID
    10706
  • Strings

    // This program demonstrates string functions.
    
    using System;
    
    class Strings 
    {
        public static void Main (string[] args) 
        {
            String str = "Hello";
    
            Console.WriteLine("string: " + str);
            Console.WriteLine("string.ToLower(): " + str.ToLower());
            Console.WriteLine("string.ToUpper(): " + str.ToUpper());
            Console.WriteLine("string.IndexOf('e'): " + str.IndexOf('e'));
            Console.WriteLine("string.Length: " + str.Length);
            Console.WriteLine("string.Replace('H', 'j'): " + str.Replace('H', 'j'));
            Console.WriteLine("string(Substring(2, 2)): " + str.Substring(2, 2));
            Console.WriteLine("string.Trim(): " + str.Trim());
    
            String name = "Bob";
            double value = 123.456;
            Console.WriteLine(String.Format("{0} earned {1:$0.00}", name, value));
        }
    }
    

    Output

    string: Hello
    string.ToLower(): hello
    string.ToUpper(): HELLO
    string.IndexOf('e'): 1
    string.Length: 5
    string.Replace('H', 'j'): jello
    string(Substring(2, 2)): ll
    string.Trim(): Hello
    Bob earned $123.46
    

    Files

    // This program creates a file, adds data to the file, displays the file,
    // appends more data to the file, displays the file, and then deletes the file.
    // It will not run if the file already exists.
    //
    // References:
    //     https://www.mathsisfun.com/temperature-conversion.html
    //     https://en.wikibooks.org/wiki/C_Sharp_Programming
    
    using System;
    
    public class Files
    {
        public static void Main(String[] args)
        {
            string FILENAME = "~file.txt";
        
            if(System.IO.File.Exists(FILENAME))
            {
                System.Console.WriteLine("File already exists.\n");
            }
            else
            {
                CreateFile(FILENAME);
                ReadFile(FILENAME);
                AppendFile(FILENAME);
                ReadFile(FILENAME);
                DeleteFile(FILENAME);
            }
        }
        
        private static double CalculateFahrenheit(double celsius)
        {
            double fahrenheit;
    
            fahrenheit = celsius * 9 / 5 + 32;
            return fahrenheit;
        }
    
        private static void CreateFile(string filename)
        {
            System.IO.StreamWriter file;
            double celsius;
            double fahrenheit;
            
            try
            {
                file = System.IO.File.CreateText(filename);
                file.WriteLine("Celsius,Fahrenheit");
                for(celsius = 0; celsius <= 50; celsius++)
                {
                    fahrenheit = CalculateFahrenheit(celsius);
                    file.WriteLine(String.Format("{0:F1},{1:F1}", celsius, fahrenheit));
                }
                file.Close();
            }
            catch(Exception exception)
            {
                Console.WriteLine("Error creating " + filename);
                Console.WriteLine(exception.Message);
            }
        }
        
        private static void ReadFile(string filename)
        {
            System.IO.StreamReader file;
            string line;
    
            try
            {
                file = System.IO.File.OpenText(filename);
                while (true) 
                {
                    line = file.ReadLine();
                    if (line == null)
                    {
                        break;
                    }
                    Console.WriteLine(line);
                }
                file.Close();
                Console.WriteLine("");
            }
            catch(Exception exception)
            {
                Console.WriteLine("Error reading " + filename);
                Console.WriteLine(exception.Message);
            }
        }
        
        private static void AppendFile(string filename)
        {
            System.IO.StreamWriter file;
            double celsius;
            double fahrenheit;
            
            try
            {
                file = System.IO.File.AppendText(filename);
                for(celsius = 51; celsius <= 100; celsius++)
                {
                    fahrenheit = CalculateFahrenheit(celsius);
                    file.WriteLine(String.Format("{0:F1},{1:F1}", celsius, fahrenheit));
                }
                file.Close();
            }
            catch(Exception exception)
            {
                Console.WriteLine("Error appending to " + filename);
                Console.WriteLine(exception.Message);
            }
        }
        
        private static void DeleteFile(string filename)
        {
            try
            {
                System.IO.File.Delete(filename);
            }
            catch(Exception exception)
            {
                Console.WriteLine("Error deleting " + filename);
                Console.WriteLine(exception.Message);
            }
        }
    }
    

    Output

    Celsius,Fahrenheit
    0.0,32.0
    1.0,33.8
    2.0,35.6
    ...
    98.0,208.4
    99.0,210.2
    100.0,212.0