C# Language MacDonald Ch. 2

1. C# LanguageMacDonald Ch. 2 MIS 324 Professor Sandvig

2. Overview • C# Basics • Variables • Datatype Conversion • Control Structures • Methods

3. C# Basics • Many similarities to PHP • Case sensitive • Curly brackets • Statements end with semi-colons; • double equal signs to test equality • if (i == 3) … • Comments: // single line /* Multi-line comment like this */

4. Variables • Declaring Variables • C# strongly typed • Similar to VB.NET • PHP loosely typed • Strongly typed: • A variable accepts only one data type • Type is explicitly declared when variable is declared

5. Variables • Strongly Typed • Advantage • Less error prone • Compiler more likely to catch programming errors • Disadvantage • Many explicit data type conversions

6. Variables • Declaring Variables • string Name; • int Age; • Declare & assign value • string Name = “Joe”; • int Age = 6;

7. Variables • Commonly Used C# Data Types

8. Variables • Variables are objects • Have all properties & methods of class • Defined in “System” namespace • String documentation

9. Variables Example: • C# declaration: string FName = “Sam”; • “FName” is string object • Has all attributes of string class • Use string replace method: FName = FName.Replace(“S”,”P”);

10. Variables IDE is very helpful:

11. Concatenation • Concatenate strings with + string Name = lastName + “, “ + firstName; • End of statement • Semicolen;

12. Datatype Conversion • C# strongly typed language • Data types must be explicitly converted • Several ways to convert data types • Convert Class • most robust • easy to use

13. Datatype Conversion Convert Class decimal TaxRate = Convert.ToDecimal(8.15);

14. Datatype Conversion • All server controls return type string:

15. Datatype Conversion Solution: Re-cast to type double:

16. Outline • C# Basics • Variables • Datatype Conversion • Control Structures • Methods

17. Control Structures • Syntax similar to PHP, Java, C, C++, … • Curley brackets for statement blocks if (condition) { //Statement block } else { //statement block }

18. Control Structures • May omit brackets for single statements: if (condition) statement 1; else statement 2;

19. Control Structures • Testing conditions • Equality • double equal sign • if (age == 3) • Inequality • if (age > 3) • Negate • if (age != 3) • AND / OR • && and • || or

20. Control Structures • Control Statements: • if • for • foreach • while

21. Control Structures • 1. if else if (condition) { //do something } else if (condition) { //do something } else { //do something else }

22. Control Structures • 2. for statement • increments a counter variable • may declare within statement for (int i = 0; i <= 10; i++) { lblMessage.Text += i + "<br>"; }

23. Control Structures • 3. foreach loop • iterate through collections • arrays, controls, cookies, etc. int[] intArray = {3, 5, 7, 9, 11}; int sum = 0; foreach (int item in intArray) { sum += item; }

24. Control Structures • 4. while loop int i = 0; while (i < 5) { i += 1; }

25. Overview • C# Basics • Variables • Datatype Conversion • Control Structures • Methods

26. Methods • Also known as: • Subroutines in VB • Functions in PHP • Chunks of code that do something useful • Pass parameters in, return a result intmyDoubler(intAnyInteger) { return AnyInteger* 2; }

27. Methods • return “void” if no value returned • void = “empty” void page_load() { //page_load is a page event }

28. Example • CSharp.aspx • Output • Source

29. Summary • C# modern object oriented programing language • Many features that we do not use in 324 • C-like syntax (similar toPHP, JavaScript) • Strongly typed • Explicitly convert data types • Pick up syntax quickly • Visual Studio big help