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Chapter 1

Chapter 1. C# Data type. Install .NET 2003 or 2005.

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Chapter 1

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  1. Chapter 1 C# Data type

  2. Install .NET 2003 or 2005 NET 2005 is better than NET 2003 and very friendly for programmer. However, NET 2005 needs NET platform 2 and NET 2003 only needs NET platform 1. The current XP system is NET platform 1 from PC manufacturer. So NET 2003 program application can directly run in current XP system. On the PC update to NET platform 2, NTE 2005 application can run. So in many case, I wrote programs in 2005. When its done, I recompile with 2003. Then the user can use my program immediately.

  3. Major C# Data Type Most of them are same as in C++

  4. What is C#? • C# is simple C++ and the easy C++. • C# is interpret program language or call manaded language. • C# has the version 7 and 8 following Visual studio 6. • C# is the future default language for window programming. • In most case, we do not use pointer in C#, which means we do not directly access the memory. However, in some case, in order to speed program, we can access the memory too, such as manage picture data. This call unsafe mode. • In C#, like in Java, it has system garbage collection to handle the memory block s which is no longer used by programs. However, we still can call Dispose() method to remove object data. • In C#, we still use reference, the key word is ref. • C# is similar to VB NET, but looks more clear.

  5. Class Definition in C++ class rectangle { private: double length; double width; public: rectangle() { length=0; width=0 ;} rectangle(double len, double wide) {length=len; width=wide; } ~rectangle() {} double getLength() { return length; } double getWidth() { return width; } double getArea() { return length * width; } void set(double len, double wide) {length = len, width = wide;} };

  6. Remarks Every class has 3 parts : • constructors and destructor constructors could be more than one (overloaded constructors) however, destructor only has one • member functions (or call methods) • member variables constructors and destructor has no type Usually functions are public and variables are private. By default variables and functions are private.

  7. Class Definition in C# class rectangle { private double length; private double width; public rectangle() { length=0; width=0 ;} public rectangle(double len, double wide) {length=len; width=wide; } public double getLength() { return length; } publicdouble getWidth() { return width; } publicdouble getArea() { return length * width; } publicvoid set(double len, double wide) {length = len, width = wide;} };

  8. class string Class String or string represents text as a series of characters. Constructors and methods string msg = new string("hello"); string msg = "hello"; Char c = msg.Char(2); int n = msg.Length; string str = string.Empty;  stringstr= ""; string stringCopy(str) int CompareTo(str) int IndexOf(str) int LastIndexOf(str) ToLower(),ToUpper(), Trim() string msg = "Good" +" Morning";(use +) string msg = “12” + 34; =“1234” string msg = “” +(12+34); =“36”

  9. Standard Input & output Console.Read(); // read one key input Console.ReadLine(); // read line to enter or 255 keys Console.Write(); // write & stay on line Console.WriteLine(); // write and go to next line Console.Clear();// clear buffer;

  10. First C# program using System; using System.Collections.Generic; using System.Text; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Console.Write("Hello"); } } }

  11. String Split function string charStr = " ,.:"; char [] charArray = charStr.ToCharArray(); string words = "one two,three:four."; string [] split = words.Split(charArray); Basic usage is public string[] Split(params char[]); Then we can use foreach() to read this string array foreach (string s in split) { Console.WriteLine(s);}

  12. Type converting String to integer uses int32.Parse(str); String str = "1234"; try { int n = Int32.Parse(str); } catch(FormatException e) { Console.WriteLine(e.Message); } String to double uses Double.Parse(str)

  13. Array declaration and initialization An integer Array must be defined like: int [] myArray = new int[50]; string [] strs = {"Mike", "John", "Kathy"}; However declarations int myArray [] ; string strs []; are wrong! It means that [] must be before the variable of array. int [,] Box = new int [3, 2]; Loop operator foreach foreach(int n in myArray){ } foreach(string s in strs){ } is special for array.

  14. Switch operator can use strings string [] array = {"Mike", "John", "Kathy"}; foreach(string one in array) { switch(one) { case "Mike": Console.write(one); break; case "John": Console.write(one); break; case "Kathy": Console.write(one); break; default: Console.write("Not found"); } }

  15. Modify1 using System; using System.Collections.Generic; using System.Text; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { static string str = "Hello"; Console.Write(str); } } }

  16. Modify2 using System; using System.Collections.Generic; using System.Text; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { if (args.Length>0) Console.Write(args[0]); else Console.Write("Hello"); } } }

  17. Some C# Math functions No Math.Random() function

  18. Random class Random class object is used to generate random integer, random floating number or random bytes. Random rnd = new Random(); // Random object rnd int n = rnd.Next(); // Random integer int k = rnd.Next()%7; // Random integer 0-6 double d = rnd.NextDouble() // Random double number between 0.0 and 1.0 Byte[] bArray = new Byte[10]; rnd.NextBytes(bArray); // Now bArray is filled with 10 Random bytes

  19. Most operators in C++ are good for C# • =, +=, -=, *=, /= //assignment operators • ==, != // compare operators • <, <=, >, >= • +, - //signed operators • +, -, *, /, % // math operation • ++, -- • <<, >> //shift operators • &, |, ^ // bitwise AND, OR, XOR The following are new operators • Console.Readline() // standard input • Console.WriteLine() // standard output

  20. Most Branch operators in C++ are also good for C# • if(x>1 && y<2){ } • if(a<2 || b>3){ } • for loop • while loop • do while loop • switch • break in the loop • continue in the loop All those operators are exactly same as in C++ or Java Be careful that C# is case sensitive

  21. MessageBox.Show MessageBox.Show( "Missing data input", // message string "input Error", // title caption string MessageBoxButtons.OK, // button type MessageBoxIcon.Exclamation // icon ); Other buttons: MessageBoxButtons.AbortRetryIgnore MessageBoxButtons.OK MessageBoxButtons.OKCancel MessageBoxButtons.RetryCancel MessageBoxButtons.YesNo MessageBoxButtons.YesNoCancel

  22. Other icons: MessageBoxIcon.Asterisk MessageBoxIcon.Error MessageBoxIcon.Exclamation MessageBoxIcon.Hand MessageBoxIcon.Information MessageBoxIcon.None MessageBoxIcon.Question MessageBoxIcon.Stop MessageBoxIcon.Warning

  23. Return value of MessageBox The return value type of MessageBox.Show() is DialogResult which has the following values: DialogResult.Abort DialogResult.Cancel DialogResult.Ignore DialogResult.No DialogResult.None DialogResult.OK DialogResult.Retry DialogResult.Yes

  24. Type converting String to integer uses Int32.Parse(str); String str = "1234"; try { int n = Int32.Parse(str); } catch(FormatException e) { Console.WriteLine(e.Message); } String to double uses Double.Parse(str)

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