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Understanding Variables in Visual C#: Types, Scope, and Operations

Explore the fundamentals of variables in Visual C# programming. This guide includes the types of data (value and reference types), their visibility (public, private), and the concept of data scope. Learn about type casting—both implicit and explicit—as well as how to declare and initialize variables properly in a strongly typed language. Discover array handling, constants, and perform arithmetic and string operations. Example exercises will help you grasp the use of variables effectively in your programs.

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Understanding Variables in Visual C#: Types, Scope, and Operations

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  1. BİL528 – Bilgisayar Programlama II Variables

  2. Contents • Variables

  3. Variables • In your programs, you must determine the type of your data (int, string, etc.) • In object oriented programming languages, you must also determine the level of visibility of your data (public, private, etc). • This visibility is known as scope.

  4. Visual C# Data Types • In Visual C#, there are two categories of data types: • Value types • Reference types

  5. Integral Value Types

  6. Floating Value Types * Use decimal for currencies.

  7. Other Value Types

  8. Reference Types

  9. Type Casting • There are two types of type casting: Implicit and Explicit • Implicit conversions are done automatically by the compiler • Widening cast • No data loss • Example: conversion from float to double • Explicit conversions require programmers approval • Narrowing cast • Data may be lost • Example: conversion from double to float

  10. Safe Conversions

  11. Explicitly Converting Data • Simplest way is using C syntax: • double d = 2.3; • int i = (int) d; • You can also use Convert class: • double d = 2.3; • int i = Convert.ToInt32(d);

  12. Some Common Methods of Convert Class

  13. Some Common Methods of Convert Class

  14. Declaring Variables • datatypevariable_name = initial_value; • int a; • string str = "BIM211"; • double m = 10, n = 20; • long k, l = 100; • Visual C# is a strongly typed language; therefore, you must always declare the data type of a variable. • In addition, Visual C# requires that all variables be initialized before they’re used.

  15. Where to put variables? • Put variables in the class definition above the methods

  16. Arrays • string[] strMyArray; • strMyArray = new string[10]; • Accessing elements: • strMyArray[0] = "BIM211"; • strMyArray[1] = "Visual Programming";

  17. Multidimensional Arrays • int[,] intMeasurements; • intMeasurements = new int[3,2]; • Accessing elements: • intMeasurements[0, 0] = 1; • intMeasurements[2, 1] = 6;

  18. Constants • You can define constant variables whose value can not be changed during the program execution by keyword const: • const double PI = 3.14159;

  19. Exercise • Create a boolean variable to store whether a confirmation box appears or not • Change its value when “Confirm on exit” menu item is clicked • Handle the FormClosing event and write the following code: • (see next slide)

  20. FormClosing Event if (m_blnPromptOnExit) { if (MessageBox.Show(“Close the Picture Viewer program?”, “Confirm Exit”, MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.No) { e.Cancel = true; } }

  21. Arithmetic Operations • Arithmetic operations are same as C but you may prefer to read chapter 12 of the textbook.

  22. String Operations • Length • SubString() • IndexOf() • Trim(), TrimStart(), TrimEnd(), Remove() • Replace()

  23. Date/Time Operations • DateTime dateMyBirthday = new DateTime(2008,7,22); • AddDays(), AddHours(), etc. • ToLongDateString() • ToShortDateString() • ToLongTimeString() • ToShortTimeString()

  24. Date/Time Operations • DateTime.Today • DateTime.Now

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