Video: Working with the Console in C# (Bulgarian)

Topics covered:

• Printing to the Console
  • Printing Strings and Numbers
• Reading from the Console
  • Reading Characters
  • Reading Strings
  • Parsing Strings to Numeral Types
  • Reading Numeral Types
• Various Examples

Video (in Bulgarian)

Presentation Content

Printing to the Console

Printing Strings, Numeral Types and Expressions

• Console is used to display information in a text window
• Can display different values:
  • Strings
  • Numeral types
  • All primitive data types
• To print to the console use the class Console ( System.Console )

The Console Class

• Provides methods for console input and output
  • Input
    • Read (…) – reads a single character
    • ReadKey(…) _ _ – reads a combination of keys
    • ReadLine(…) – reads a single line of characters
  • Output
    • Write(…) – prints the specified argument on the console
    • WriteLine(… ) – prints specified data to the console and moves to the next line

Formatting Strings

• {index[,alignment][:formatString]}
• index
  • The zero-based index of the argument whose string representation is to be included at this position in the string
• alignment
  • A signed integer that indicates the total length of the field into which the argument is inserted
    • a positive integer – right-aligned
    • a negative integer – left-aligned
• formatString
  • Specifies the format of the corresponding argument’s result string, e.g. " X ", " C ", " 0.00 "

Reading from the Console

Reading Strings and Numeral Types

• We use the console to read information from the command line
• We can read:
  • Characters
  • Strings
  • Numeral types (after conversion)
• To read from the console we use the methods Console.Read() and Console.ReadLine()

Console.Read()

• Gets a single character from the console (after [Enter] is pressed)
  • Returns a result of type int
  • Returns -1 if there aren’t more symbols
• To get the actually read character we need to cast it to char

Console.ReadKey()

• Waits until a combination of keys is pressed
  • Reads a single character from console or a combination of keys
• Returns a result of type ConsoleKeyInfo
  • KeyChar – holds the entered character
  • Modifiers – holds the state of [Ctrl], [Alt], …

Console.ReadLine()

• Gets a line of characters
• Returns a string value
• Returns null if the end of the input is reached

Reading Numeral Types

• Numeral types can not be read directly from the console
• To read a numeral type do the following:
  • Read a string value
  • Convert (parse) it to the required numeral type
• int.Parse(string )
  • Parses (converts) a string to int

Converting Strings to Numbers

• Numeral types have a method Parse(…) for extracting the numeral value from a string
  • int.Parse(string) – string -> int
  • long .Parse(string ) – string -> long
  • float .Parse(string) – string -> float
  • Causes FormatException in case of error
• Converting can also be done using the methods of the Convert class
  • Convert.ToInt32(string) – string -> int
  • Convert.ToSingle(string ) – string -> float
  • Convert.ToInt64(string) – string -> long
  • It uses the parse methods of the numeral types

Error Handling when Parsing

• Sometimes we want to handle the errors when parsing a number
  • Two options: use try - catch block or TryParse()
• Parsing with TryParse()

How to Print Special Characters on the Console?

• Printing special characters on the console needs two steps:
  • Change the console propertiesto enable Unicode-friendly font
  • Enable Unicode for the Consoleby adjusting its output encoding
    • Prefer UTF8 (Unicode)

Decimal Separator

• The currency format and number formats are different in different countries
  • E.g. the decimal separator could be " . " or " , "
• To ensure the decimal separator is “.” use the following code:

Summary

• We have discussed the basic input and output methods of the class Console
  • Write(…) and WriteLine( … )
    • Used to write values to the console
  • Read(…) and ReadLine( … )
    • Used to read values from the console
• Parsing numbers to strings
  • int.Parse(…) , double.Parse(…) , …