Strings in C#

Overview

• Reference Data Type: Strings are a reference data type in C#.
• Storage: They are used to store sequences of character objects, representing text.
• Class: A string in C# is an object of the System.String class.
• Operations: The String class provides a wide range of methods to perform various operations on strings.

Declaration & Initialization

1. Using string Keyword:

   • Declaration:

     string name; // String declaration

   • Declaration and Initialization:

     string name = "Kamal"; // Declaration and initialization at once

2. Creating an Object from System.String Class:

   • Declaration:

     String homeTown; // Declaration

   • Declaration and Initialization:

     String homeTown = "Colombo"; // Declaration and initialization at once

Common String Methods

Here are some commonly used methods from the System.String class:

1. Clone()

   • Description: Returns a reference to this instance of the string.
   • Example:

     string original = "Hello";
     string copy = (string)original.Clone();

2. Compare(String, String)

   • Description: Compares two string objects.
   • Example:

     int result = String.Compare("Apple", "Banana");
     // result will be less than 0 because "Apple" is less than "Banana"

3. Concat(String, String)

   • Description: Concatenates two specified strings.
   • Example:

     string fullName = String.Concat("John", "Doe");
     // fullName will be "JohnDoe"

4. ToString()

   • Description: Returns an instance of the string.
   • Example:

     int number = 123;
     string numberString = number.ToString();

5. Trim()

   • Description: Removes leading and trailing whitespace characters.
   • Example:

     string text = "  Hello  ";
     string trimmedText = text.Trim(); // "Hello"

6. ToUpper()

   • Description: Converts a string into uppercase.
   • Example:

     string text = "hello";
     string upperText = text.ToUpper(); // "HELLO"

7. IndexOf(char)

   • Description: Gets the index of the specified character in the string.
   • Example:

     string text = "Hello";
     int index = text.IndexOf('e'); // index will be 1

8. Substring(Int32)

   • Description: Retrieves a substring from this instance starting at a specified index.
   • Example:

     string text = "HelloWorld";
     string subText = text.Substring(5); // subText will be "World"

9. Join(String, String[])

   • Description: Concatenates all the elements of a string array, using the specified separator.
   • Example:

     string[] words = { "Hello", "World" };
     string sentence = String.Join(" ", words); // sentence will be "Hello World"