16.1 Creating string in C#
A string is an object of type String that stores the value in the form of a text. The text is stored as a sequence of read only characters stored in an array. The string in C# contains embedded null characters (‘\O’). The string keyword in C# is an alias for String. The String class provides various string operations as creating, manipulating, concatenating and comparing the values.
String objects can be created by any of the following methods as mentioned below:
a) Assigning a string literal to a String variable
string name; name = “Jennifer”; Console.WriteLine( “The name is:”+name );
The string literal is assigned to the name variable of type string.
b) Using the string concatenation
string name, level; name = “Jennifer”; level = “MBA”; string value = name + level; Console.WriteLine( “The detail is:”+name +level ); Console.Read();
The value variable contains the concatenation of two strings as name and level respectively.
c) Using the String class constructor
static void Main) string[ ] args ) { char[ ] location = new char [7] { ‘N’, ‘e’, ‘w’, ‘Y’, ‘o’, ’r’ ,’k’}; string address1 = new string(location); Console.WriteLine(address1); Console.Read(); }
The location array contains the elements of char type. The variable of type string is used to display values.
d) Retrieving property or calling a method that returns a string
string[ ] data = new string[] {“Learn”, “Strings”, “In”, “C#”}; string output = String.Join (“ “, data); Console.WriteLine(output); Console.Read();
The Join method is used for combining the values in the string array.
e) The method used for formatting or converting the value to specific string representation
DateTime d = new DataTime (2014, 10, 1, 10, 30, 15); string values = String.Format(“Message sent on {0:t} on {0:D}”, d); Console.WriteLibe(“The value is:{0}”, values); Console.Read();
The Date and Time when the user communicated is displayed using the DateTime method of C#.
16.2 Properties of string class
The String type has two properties as mentioned below:
Type | Description |
Chars | It gets the Char object at a specified position in the current String object |
Length | It gets the number of characters in the current String object |
A code sample to demonstrate the properties in C# is as shown below:
class Program { static void Main( string[ ] args ) { string str1 = “Welcome”; for ( int c=0; c<str1.Length-1; c++); { Console.WriteLine(“{0}”, str1[c]); } Console.WriteLine(“The length of the string ‘{0}’ is {1}”, str1, str1.Length); Console.Read(); } }
The output for the code is as shown below:
16.3 Methods of string class
Some of the methods of the string class are as shown below:
Method | Description |
Clone() | It is used to make the clone of the string |
Compare() | It compares the two specified strings and returns the integer value |
Concat() | It is used for concatenation of two string objects |
Contains() | It is checks whether the specified character or string exists in the string value |
Copy() | It creates a new string object with the same value as the specified string |
EndsWith() | It is used to check whether the specified character is the last character of the string |
Equals() | It compares two strings and returns the Boolean value as output |
GetHashCode() | It returns the HashValue of the specified string |
GetType() | It returns the System.Type of the current instance |
IndexOf() | It returns the index position of the first occurrence of the specified character |
ToLower() | It converts the string into lower case |
ToUpper() | It converts the string into upper case |
Insert() | It inserts the string or character in the string at a specific position |
LastIndexOf() | It returns the index position of last occurrence of the specified character |
Remove() | It is used to delete all the characters from the beginning to the specific position |
Replace() | It is used to replace a character in the string |
Split() | It splits the string based on the specific value |
StartsWith() | It checks the first character of the string matches with the specific character |
Substring() | It is used to return the substring |
ToCharArray() | It converts the string to the character array |
Trim() | It removes the extra whitespaces from the beginning and the end of the string |
class Program { static void Main ( string[ ] args ) { string city; city = “London”; string country; country = “United Kingdom”; Console.WriteLine(city.Clone()); //The clone of the string is created Console.WriteLine(city.CompareTo(country)); //It compares the two strings and returns 0 if True else 1 for false Console.WriteLine(country.EndsWith(“m”)); //It checks whether the specified character is the last character Console.WriteLine(country.Contains(“King”)); //It checks whether the value specified is present in the string Console.WriteLine(city.Equals(country)); //It compares the two strings and returns to true or false Console.WriteLine(city.CompareTo(country)); //It is used for the comparison of two strings Console.WriteLine(country.GetHashCode()); //It is used for returning the Hash code for the string Console.WriteLine(country.ToLower()); //It converts the string to Lower case Console.WriteLine(city.ToUpper()); //It converts the string to upper case Console.WriteLine(country.Insert ( 0, “A”)); //Inserts the value at the specified position Console.WriteLine(city.LastIndexOf(“n”)); //Returns the last index value of the specified value Console.WriteLine(country.Remove(6)); //Removes the character from the specified position Console.WriteLine(city.StartsWith(“L”)); //Returns the first character of the string with the specified value Console.WriteLine(country.Substring(3,4)); //Returns the substring of the specified string Console.WriteLine(country.Trim()); //removes the starting and ending whitespaces in the string string[ ] split = city.Split(new char[] {“0”}); Console.WriteLine(split[0]); Console.WriteLine(split[2]); Console.Read(); } }
Sample code for demonstrating the methods of string class in C# is as shown below:
The output for the code is as shown below:
16.4 Example of string in C#
class Program { static void Main ( string[ ] args ) { string s1 = “Strings are literals”; string s2 = “Values are assigned to the variables”; s1 = s1 + s2; Console.WriteLine(s1); string s3 = “Reverse letters”; for ( int i=0; i<14; i++) { Console.WriteLine(s3[ s3.Length – i – 1] ); } string [ ] data = { “C# data”, “Array data”, “collection of data”}; string pattern = “data”; foreach ( string s in data ) { Console.Write(“{0,9}”, s); if ( System.Text.RegularExpression.Regex.IsMatch ( s, pattern , System.Text.RegularExpressions.RegexOptions.IgnoreCase) ); { Console.WriteLine((“match for {0} found), pattern ); } else { Console.WriteLine(); } } } Console.Read(); }
A sample code to demonstrate the string functionality in C# is as shown below:
The output for the code is as shown below:
In the above code, the concatenation, reverse of string and identifying values through regular expressions is performed on different string variables. The output received after applying various functions is as shown above.