string str = "abcde";
char ch = str[1]; // ch == 'b'
str[1] = 'a'; // Compilation error!
ch = str[50]; // IndexOutOfRangeException

string a="Hello \"C#\"";
string b="Hello \r\n C#"; //مساوی با اینتر
string c="C:\\a.jpg"; //چاپ خود علامت  \ -مسیردهی

string c=@"C:\a.jpg";// == "C:\\a.jpg"

string source = "Some source";
string assigned = source;

string hel = "Hel";
string hello = "Hello";
string copy = hel + "lo";

string hello = "Hello";
string same = "Hello";

Console.WriteLine(word1.Equals(word2,
    StringComparison.CurrentCultureIgnoreCase));

string score = "sCore";
string scary = "scary";
 
Console.WriteLine(score.CompareTo(scary));
Console.WriteLine(scary.CompareTo(score));
Console.WriteLine(scary.CompareTo(scary));
 
// Console output:
// 1
// -1
// 0

string alpha = "alpha";
string score1 = "sCorE";
string score2 = "score";
 
Console.WriteLine(string.Compare(alpha, score1, false));
Console.WriteLine(string.Compare(score1, score2, false));
Console.WriteLine(string.Compare(score1, score2, true));
Console.WriteLine(string.Compare(score1, score2,
    StringComparison.CurrentCultureIgnoreCase));
// Console output:
// -1
// 1
// 0
// 0

string doc = "Smith's number: 0898880022\nFranky can be " +
    "found at 0888445566.\nSteven's mobile number: 0887654321";
string replacedDoc = Regex.Replace(
    doc, "(08)[0-9]{8}", "$1********");
Console.WriteLine(replacedDoc);
// Console output:
// Smith's number: 08********
// Franky can be found at 08********.
// Steven' mobile number: 08********

 DateTime dt = DateTime.Now;
            string s = "";
        for (int index = 1; index <= 20000; index++)
        {
            s += index.ToString();
        }
            Console.WriteLine(s);
            Console.WriteLine(dt);
            Console.WriteLine(DateTime.Now);
            Console.ReadKey();

string declared = "Intern pool";
string built = new StringBuilder("Intern pool").ToString();

 StringBuilder sb = new StringBuilder();
      sb.Append("Numbers: ");

            DateTime dt = DateTime.Now;
        for (int index = 1; index <= 200000; index++)
        {
            sb.Append(index);
        }
            Console.WriteLine(sb.ToString());
            Console.WriteLine(dt);
            Console.WriteLine(DateTime.Now);
            Console.ReadKey();

StringBuilder sb = new StringBuilder(15);
sb.Append("Hello, C#!");

DateTime date = DateTime.Now;
string name = "David Scott";
string task = "Introduction to C# book";
string location = "his office";
 
string formattedText = String.Format(
    "Today is {0:MM/dd/yyyy} and {1} is working on {2} in {3}.",
    date, name, task, location);
Console.WriteLine(formattedText);