C# provides several methods for string manipulation, which can be quite handy in various programming scenarios. Here are some common string manipulation methods:

1. Concatenation

• String.Concat or + operator: Combines multiple strings.

string str1 = "Hello";
string str2 = "World";
string combined = string.Concat(str1, " ", str2); // "Hello World"
// Or using the + operator
string combined = str1 + " " + str2; // "Hello World"

2. Substring

• Substring(int startIndex) and Substring(int startIndex, int length): Extracts a portion of the string.

string text = "Hello World";
string substring = text.Substring(0, 5); // "Hello"

3. Replace

• Replace(string oldValue, string newValue): Replaces occurrences of a specified string in the input string.

string text = "Hello World";
string replaced = text.Replace("World", "C#"); // "Hello C#"

4. Trim

• Trim(), TrimStart(), TrimEnd(): Removes whitespace from the beginning and/or end of the string.

string text = "  Hello World  ";
string trimmed = text.Trim(); // "Hello World"

5. ToUpper and ToLower

• ToUpper() and ToLower(): Converts all characters in the string to uppercase or lowercase.

string text = "Hello World";
string upper = text.ToUpper(); // "HELLO WORLD"
string lower = text.ToLower(); // "hello world"

6. Split and Join

• Split(char separator): Splits the string into an array of substrings based on a delimiter.

• Join(string separator, string[] value): Combines an array of strings into a single string with a delimiter.

string text = "Hello,World,from,C#";
string[] words = text.Split(','); // ["Hello", "World", "from", "C#"]
string joined = string.Join(" ", words); // "Hello World from C#"

7. Contains

• Contains(string value): Checks if the string contains a specified substring.

string text = "Hello World";
bool containsWorld = text.Contains("World"); // true

8. IndexOf and LastIndexOf

• IndexOf(char value) and LastIndexOf(char value): Returns the index of the first and last occurrence of a character in the string.

string text = "Hello World";
int index = text.IndexOf('o'); // 4
int lastIndex = text.LastIndexOf('o'); // 7

9. StartsWith and EndsWith

• StartsWith(string value) and EndsWith(string value): Checks if the string starts or ends with a specified substring.

string text = "Hello World";
bool startsWithHello = text.StartsWith("Hello"); // true
bool endsWithWorld = text.EndsWith("World"); // true

10. Format

• String.Format(format, args): Inserts arguments into a string with placeholders.

string formatted = string.Format("Name: {0}, Age: {1}", "Alice", 30); // "Name: Alice, Age: 30"

These are just a few examples of the many string manipulation methods available in C#. If you need more details or specific use cases, feel free to ask!