.Net Programming with C#

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1 .Net Programming with C#
Haiming Chen Department of Computer Science Ningbo University Fall Semester , Course 106F22A01

2 Data type in C# Type Description Range/Precision Example bool ulong
Boolean type true, false bool val1 = true; bool val2 = false; short 16-bit signed integer –32, ,767 short val = 12; int 32-bit signed integer –2,147,483, ,147,483,647 int val = 12; long 64-bit signed integer –9,223,372,036,854,775,808 ...9,223,372,036,854,775,807 long val1 = 12; long val2 = 34L; byte 8-bit unsigned integer byte val1 = 12; byte val2 = 34U; ushort 16-bit unsigned integer 0...65,535 ushort val1 = 12; ushort val2 = 34U; uint 32-bit unsigned integer 0...4,294,967,295 uint val1 = 12; uint val2 = 34U; ulong 64-bit unsigned integer 0...18,446,744,073,709,551,615 ulong val1 = 12; ulong val2 = 34U; ulong val3 = 56L; ulong val4 = 78UL;

3 Data type in C# Type Description Range/Precision Example float char
decimal Precise decimal type 1.0 × 10−28 至 7.9 × 1028，28-figure precision decimal val = 1.23M; float Single-precision float type 1.5 × 10−45 至 3.4 × 1038，7-figure precision float val = 1.23F; double Double-precision float type 5.0 × 10−324 至 1.7 × 10308，15-figure precision double val1 = 1.23; double val2 = 4.56D; char A character letters, digits, and special characters, like ‘#’, ‘$’, which has a Unicode char val1 = 'h'; char val2 = ‘\’’; char val3 = ‘\\’ char val4 = ‘\uhhhh’; string A series of characters string s= "Hello";

4 String Operation Join Extract character or substring
string str=“aaa”+”bbb”; string str=“aaa”+’1’; string str=“aaa”+1; string str=“aaa”+1.23M; Extract character or substring char c=str[0]; string subStr= str. Substring(0,3); // Substring(4); int index = str. IndexOf(“b”); // LastIndexOf(“b”); 1 2 3 4 5 6 a b 1

5 String Operation Compare
str1.CompareTo (str2); // -1 means str1<str // 1 means str1>str // 0 means str1==str2 str1. Equals (str2); Remove leading and trailing white-space characters str1.Trim();

6 String Operation Convert string to number Convert number to string
int num = int.Parse(“123”); float num = float.Parse(“ ”); Convert number to string string str = num.ToString(); string str = string. Format (“{0}”, num);

7

8 Array type [,…] array_name = new type [n,…];
int [] intArray = new int [3]; short [] shortArray = new short []{1,2,3} string [] strArray = {“Ning”, “ ”, “bo”}; string [] strArray; // declaration strArray = new string [3]; // initialization strArray = {“Ning”, “ ”, “bo”}; //set value, error strArray[0] = “Ning”; strArray[1] = “ “; strArray[2] = “bo”; Ning bo

9 Array Operation GetLength(); GetValue(index);
SetValue (newValue, index) CopyTo(newArray, fromIndex); Convert string to string array str.Split(‘separator character’); Convert string array to string string.Join (“separator string”, string_array)

10 Example Change the string “Ningbo Zhejiang China” to “Ningbo, Zhejiang, China” string str= “Ningbo Zhejiang China”; int indexSpace=str.IndexOf(“ “); str[indexSpace]=‘,’; // error Note: Each character in a string cannot be changed separately.

11 Overview Data types in C# Define variables Define constants
Value types (char, int, long, short, float, double,…) String Array Define variables Declare Initialize Define constants const float _pi = F Do them at the same time