Csharp/CSharp Tutorial/String/String

Basic String functionality

<source lang="csharp">using System; using System.Collections.Generic; using System.Text;

 class Program
 {
   static void Main(string[] args)
   {
     string firstName = "Buddy";
     Console.WriteLine("Value of firstName: {0}", firstName);
     Console.WriteLine("firstName has {0} characters.", firstName.Length);
     Console.WriteLine("firstName in uppercase: {0}", firstName.ToUpper());
     Console.WriteLine("firstName in lowercase: {0}", firstName.ToLower());
     Console.WriteLine("firstName contains the letter y?: {0}", firstName.Contains("y"));
     Console.WriteLine("firstName after replace: {0}", firstName.Replace("dy", ""));
   }
 }</source>

Declaration of string

1. strings are objects.
2. string is a reference type.

1. static string Copy(string str)
2. int CompareTo(string str)
3. int IndexOf(string str)
4. int LastIndexOf(string str)
5. string ToLower( )
6. string ToUpper( )

A string is a set of characters enclosed by double quotes. For example,

<source lang="csharp">"this is a test"</source>

Display all the characters in myString using a for loop

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   string myString = "To be or not to be";
   
   for (int count = 0; count < myString.Length; count++)
   {
     Console.WriteLine("myString[" + count + "] = " + myString[count]);
   }
 }

}</source>

myString[0] = T
myString[1] = o
myString[2] =
myString[3] = b
myString[4] = e
myString[5] =
myString[6] = o
myString[7] = r
myString[8] =
myString[9] = n
myString[10] = o
myString[11] = t
myString[12] =
myString[13] = t
myString[14] = o
myString[15] =
myString[16] = b
myString[17] = e

Empty string

<source lang="csharp">using System; using System.IO; using System.Text; public class MainClass {

   public static void Main(string[] args)
   {
       string address = String.Empty;
   }

}</source>

Error; string Is Immutable

<source lang="csharp">class Uppercase {

 static void Main()
 {
     string text;
     System.Console.Write("Enter text: ");
     text = System.Console.ReadLine();
     text.ToUpper();
     System.Console.WriteLine(text);
 }

}</source>

String are immutable

<source lang="csharp">using System; using System.Collections.Generic; using System.Text;

 class Program
 {
   static void Main(string[] args)
   {
     // Set initial string value.
     string s1 = "This is my string.";
     Console.WriteLine("s1 = {0}", s1);
     // Uppercase the s1?
     string upperString = s1.ToUpper();
     Console.WriteLine("upperString = {0}", upperString);
     // Nope!  s1 is in the same format!
     Console.WriteLine("s1 = {0}", s1);
     string s2 = "My other string";
     s2 = "New string value";
   }
 }</source>

String is object

<source lang="csharp">using System; class MainClass {

   static void Main(string[] args) {
       string strOriginal = "Original String";
       Console.WriteLine( "Value of strOriginal before call: {0}", strOriginal );
       TryToAlterString( strOriginal );
       Console.WriteLine( "Value of strOriginal after call: {0}", strOriginal );
   }
   static void TryToAlterString(string str) {
       str = "Modified String";
   }

}</source>

Value of strOriginal before call: Original String
Value of strOriginal after call: Original String

Use Indexer to reference chars in a string

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   string myString = "To be or not to be";
   
   for (int count = 0; count < myString.Length; count++)
   {
     Console.WriteLine("myString[" + count + "] = " + myString[count]);
   }
 }

}</source>

myString[0] = T
myString[1] = o
myString[2] =
myString[3] = b
myString[4] = e
myString[5] =
myString[6] = o
myString[7] = r
myString[8] =
myString[9] = n
myString[10] = o
myString[11] = t
myString[12] =
myString[13] = t
myString[14] = o
myString[15] =
myString[16] = b
myString[17] = e

Use the addition operator (+) to concatenate strings

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   string myString6 = "To be, " + "or not to be";
   Console.WriteLine("\"To be, \" + \"or not to be\" = " + myString6);
 }

}</source>

"To be, " + "or not to be" = To be, or not to be

Use the Compare() method to compare strings

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   
   int result;
   result = String.rupare("bbc", "abc");
   Console.WriteLine("String.rupare(\"bbc\", \"abc\") = " + result);
   result = String.rupare("abc", "bbc");
   Console.WriteLine("String.rupare(\"abc\", \"bbc\") = " + result);
   result = String.rupare("bbc", "bbc");
   Console.WriteLine("String.rupare(\"bbc\", \"bbc\") = " + result);
   result = String.rupare("bbc", "BBC", true);
   Console.WriteLine("String.rupare(\"bbc\", \"BBC\", true) = " + result);
   result = String.rupare("bbc", "BBC", false);
   Console.WriteLine("String.rupare(\"bbc\", \"BBC\", false) = " + result);
   result = String.rupare("Hello World", 6, "Goodbye World", 8, 5);
   Console.WriteLine("String.rupare(\"Hello World\", 6, " + "\"Goodbye World\", 8, 5) = " + result);
 }

}</source>

String.rupare("bbc", "abc") = 1
String.rupare("abc", "bbc") = -1
String.rupare("bbc", "bbc") = 0
String.rupare("bbc", "BBC", true) = 0
String.rupare("bbc", "BBC", false) = -1
String.rupare("Hello World", 6, "Goodbye World", 8, 5) = 0

Use the Concat() method to concatenate strings

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   string myString4 = String.Concat("A, ", "B");
   Console.WriteLine("String.Concat(\"A, \", \"B\") = "+ myString4);
   string myString5 = String.Concat("A, ", "B, ", "and countrymen");
   Console.WriteLine("String.Concat(\"A, \", \"B, \", " + "\"and countrymen\") = " + myString5);
 }

}</source>

String.Concat("A, ", "B") = A, B
String.Concat("A, ", "B, ", "and countrymen") = A, B, and countrymen

Use the Copy() method to copy a string

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   
   string myString4 = "string4";
   Console.WriteLine("myString4 = " + myString4);
   Console.WriteLine("Copying myString4 to myString7 using Copy()");
   string myString7 = String.Copy(myString4);
   Console.WriteLine("myString7 = " + myString7);
 }

}</source>

myString4 = string4
Copying myString4 to myString7 using Copy()
myString7 = string4

Use the Equals() method and equality operator to check if two strings are equal

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   bool boolResult;
   string myString = "str";
   string myString2 = "str2";
   
   boolResult = String.Equals("bbc", "bbc");
   Console.WriteLine("String.Equals(\"bbc\", \"bbc\") is " + boolResult);
   
   boolResult = myString.Equals(myString2);
   Console.WriteLine("myString.Equals(myString2) is " + boolResult);
   
   boolResult = myString == myString2;
   Console.WriteLine("myString == myString2 is " + boolResult);
 }

}</source>

String.Equals("bbc", "bbc") is True
myString.Equals(myString2) is False
myString == myString2 is False

Use the Format() method to format a string

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   
   float myFloat = 1234.56789f;
   string myString8 = String.Format("{0, 10:f3}", myFloat);
   Console.WriteLine("String.Format(\"{0, 10:f3}\", myFloat) = " + myString8);
 }

}</source>

String.Format("{0, 10:f3}", myFloat) =   1234.568

Use the IndexOfAny() and LastIndexOfAny() methods to search for character arrays in a string

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   string[] myStrings = {"To", "be", "or", "not", "to", "be"};
   string myString = String.Join(".", myStrings);   
   
   char[] myChars = {"b", "e"};
   int index = myString.IndexOfAny(myChars);
   Console.WriteLine(""b" and "e" occur at index " + index + " of myString");
   index = myString.LastIndexOfAny(myChars);
   Console.WriteLine(""b" and "e" last occur at index " + index + " of myString");
 }

}</source>

"b" and "e" occur at index 3 of myString
"b" and "e" last occur at index 17 of myString

Use the Insert(), Remove(), and Replace() methods to modify strings

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   string[] myStrings = {"To", "be", "or", "not", "to", "be"};
   string myString = String.Join(".", myStrings);   
   
   string myString10 = myString.Insert(6, "A, ");
   Console.WriteLine("myString.Insert(6, \"A, \") = " + myString10);
   string myString11 = myString10.Remove(14, 7);
   Console.WriteLine("myString10.Remove(14, 7) = " + myString11);
   string myString12 = myString11.Replace(",", "?");
   Console.WriteLine("myString11.Replace(",", "?") = " + myString12);
   string myString13 = myString12.Replace("to be", "Or not to be A");
   Console.WriteLine("myString12.Replace(\"to be\", \"Or not to be A\") = " + myString13);
 }

}</source>

myString.Insert(6, "A, ") = To.be.A, or.not.to.be
myString10.Remove(14, 7) = To.be.A, or.no
myString11.Replace(",", "?") = To.be.A? or.no
myString12.Replace("to be", "Or not to be A") = To.be.A? or.no

Use the Join() method to join strings

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   
   string[] myStrings = {"To", "be", "or", "not", "to", "be"};
   string myString9 = String.Join(".", myStrings);
   Console.WriteLine("myString9 = " + myString9);
 }

}</source>

myString9 = To.be.or.not.to.be

Use the PadLeft() and PadRight() methods to align strings

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   string[] myStrings = {"To", "be", "or", "not", "to", "be"};
   string myString = String.Join(".", myStrings);   
   
   string myString14 = "(" + myString.PadLeft(20) + ")";
   Console.WriteLine(""(" + myString.PadLeft(20) + ")" = " + myString14);
   string myString15 = "(" + myString.PadLeft(20, ".") + ")";
   Console.WriteLine(""(" + myString.PadLeft(20, ".") = " + myString15);
   string myString16 = "(" + myString.PadRight(20) + ")";
   Console.WriteLine(""(" + myString.PadRight(20) + ")" = " + myString16);
   string myString17 = "(" + myString.PadRight(20, ".") + ")";
   Console.WriteLine(""(" + myString.PadRight(20, ".") + ")" = " + myString17);
 }

}</source>

"(" + myString.PadLeft(20) + ")" = (  To.be.or.not.to.be)
"(" + myString.PadLeft(20, ".") = (..To.be.or.not.to.be)
"(" + myString.PadRight(20) + ")" = (To.be.or.not.to.be  )
"(" + myString.PadRight(20, ".") + ")" = (To.be.or.not.to.be..)

Use the Split() method to split strings

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   string[] myStrings = {"To", "be", "or", "not", "to", "be"};
   string myString9 = String.Join(".", myStrings);    
   myStrings = myString9.Split(".");
   foreach (string mySplitString in myStrings)
   {
     Console.WriteLine("mySplitString = " + mySplitString);
   }
 }

}</source>

mySplitString = To
mySplitString = be
mySplitString = or
mySplitString = not
mySplitString = to
mySplitString = be

Use the Substring() method to retrieve substrings

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   
   string[] myStrings = {"To", "be", "or", "not", "to", "be"};
   string myString = String.Join(".", myStrings);   
   
   
   string myString21 = myString.Substring(3);
   Console.WriteLine("myString.Substring(3) = " + myString21);
   string myString22 = myString.Substring(3, 2);
   Console.WriteLine("myString.Substring(3, 2) = " + myString22);
 }

}</source>

myString.Substring(3) = be.or.not.to.be
myString.Substring(3, 2) = be

Use the Trim(), TrimStart(), and TrimEnd() methods to trim strings

<source lang="csharp">using System; class MainClass {

 public static void Main()
 {
   
   string myString18 = "(" + "  Whitespace  ".Trim() + ")";
   Console.WriteLine(""(" + \"  Whitespace  \".Trim() + ")" = " + myString18);
   string myString19 = "(" + "  Whitespace  ".TrimStart() + ")";
   Console.WriteLine(""(" + \"  Whitespace  \".TrimStart() + ")" = " + myString19);
   string myString20 = "(" + "  Whitespace  ".TrimEnd() + ")";
   Console.WriteLine(""(" + \"  Whitespace  \".TrimEnd() + ")" = " + myString20);
 }

}</source>

"(" + "  Whitespace  ".Trim() + ")" = (Whitespace)
"(" + "  Whitespace  ".TrimStart() + ")" = (Whitespace  )
"(" + "  Whitespace  ".TrimEnd() + ")" = (  Whitespace)

Working with Strings

<source lang="csharp">class Uppercase {

 static void Main()
 {
     System.Console.Write("Enter text: ");
     var text = System.Console.ReadLine();
     var uppercase = text.ToUpper();
     System.Console.WriteLine(uppercase);
 }

}</source>