//1.声明字符串，没有初始化string message1;

//2.使用null初始化字符串string message2 = null;

//3.使用Empty初始化字符串,可新建字符串长度为零的String对象。//零长度字符串的字符串表示形式为""。//使用Empty值（而不是null）初始化字符串可以降低发生NullReferenceException的可能性string message3 = String.Empty;

//4.初始化一个普通的字符串string oldPath = "c:\\Program Files\\Microsoft";

//5.初始化一个逐字字符串string newPath = @"c:\Program Files\Microsoft";

//6.本地变量（即在方法体）,你可以使用隐式类型。var temp = "I'm still a ...";

//7.除了在使用字符数组初始化字符串以外，不要使用new运算符创建字符串对象。char[] letters = {'A','B','C'};string alphabet = new string(letters);

//在下面的示例中，当连接s1和s2的内容形成一个字符串时，不会修改两个原始字符串。//+=运算符会创建一个包含组合内容的新字符串。这个新对象赋给变量s1，而最初赋给//s1的对象由于没有其他任何变量包含对它的引用而释放，用于垃圾回收。string s1 = "A string is more";string s2 = "than the sum of its chars.";s1 += s2;System.Console.WriteLine(s1);//Output:A string is more than the sum of its chars.

string s1 = "Hello";string s2 = s1;s1 += "World";System.Console.WriteLine(s2);//Output:Hello

string columns = "Column 1\tColumn 2\tColumn 3";//Output: Column 1        Column 2        Column 3

string rows = "Row 1\r\nRow 2\r\nRow 3";/* Output:  Row 1  Row 2  Row 3*/

string title = "\"The \u00C6olean Harp\", by Samuel Taylor Coleridge";//Output: "The Æolean Harp", by Samuel Taylor Coleridge

string filePath = @"C:\Users\scoleridge\Documents\";//Output: C:\Users\scoleridge\Documents\

string text = @"My pensive SARA ! thy soft cheek reclined    Thus on mine arm, most soothing sweet it is    To sit beside our Cot,...";/* Output:My pensive SARA ! thy soft cheek reclined   Thus on mine arm, most soothing sweet it is   To sit beside our Cot,... */

string quote = @"Her name was ""Sara.""";//Output: Her name was "Sara."

string s5 = "Printing backwards";for(int i = 0; i < s5.Length; i++){    System.Console.Write(s5[s5.Length - i - 1]);}//Output:"sdrawkcab gnitnirP"

string question = "hOW DOES mICROSOFT wORD DEAL WITH THE cAPS lOCK KEY?";System.Text.StringBuilder sb = new System.Text.StringBuilder(question);

for (int j = 0; j < sb.Length; j++){if (System.Char.IsLower(sb[j]) == true)    {        sb[j] = System.Char.ToUpper(sb[j]);    }else if (System.Char.IsUpper(sb[j]) == true)    {        sb[j] = System.Char.ToLower(sb[j]);    }}// Store the new string.string corrected = sb.ToString();System.Console.WriteLine(corrected);// Output: How does Microsoft Word deal with the Caps Lock key?   

static void Main(){string str = "hello";string nullStr = null;string emptyStr = String.Empty;

string tempStr = str + nullStr;// The following line displays "hello." Console.WriteLine(tempStr);

bool b = (emptyStr == nullStr);// The following line displays False. Console.WriteLine(b);

// The following line creates a new empty string. string newStr = emptyStr + nullStr;

// Null strings and empty strings behave differently. The following// two lines display 0. Console.WriteLine(emptyStr.Length);    Console.WriteLine(newStr.Length);// The following line raises a NullReferenceException.//Console.WriteLine(nullStr.Length);

// The null character can be displayed and counted, like other chars. string s1 = "\x0" + "abc";string s2 = "abc" + "\x0";// The following line displays "* abc*". Console.WriteLine("*" + s1 + "*");// The following line displays "*abc *". Console.WriteLine("*" + s2 + "*");// The following line displays 4. Console.WriteLine(s2.Length);}