What is a String in .NET?
💡 Concept Name
String — A string is a data structure that stores a series of characters as a single value, often used to represent words, sentences, or any text in programming.
📘 Quick Intro
Strings are the backbone of text processing in every programming language. In .NET, a string is an object that holds an ordered sequence of characters—letters, numbers, or symbols—all accessible by a numeric index starting from 0.
🧠 Analogy / Short Story
Imagine a string as a necklace of alphabet beads: each bead represents a character, and you can refer to each by its position from the clasp. The whole necklace is your string—organized, counted, and easily accessible.
🔧 Technical Explanation
- 🔢 Indexing: Characters in a string are zero-indexed—first character is at index 0.
- 🔒 Immutability: Strings in .NET are immutable—changing a string creates a new object in memory.
- 🌍 Unicode Support: .NET strings use UTF-16 encoding, supporting global languages and emojis.
- ⚡ Fast Access: Characters can be accessed directly by index, e.g.,
str[0]. - 📦 Object Type:
stringin .NET is an alias forSystem.String, stored on the managed heap.
🎯 Purpose & Use Case
- ✅ Storing and displaying names, messages, addresses, or any textual data.
- ✅ Parsing user input, formatting output, or performing search and replace operations.
- ✅ Logging application events or errors, file path management, and command-line arguments.
💻 Real Code Example
// Declaring and using strings in C#
string welcome = "Hello";
Console.WriteLine(welcome[0]); // Output: H
// Concatenation
welcome = welcome + " World";
Console.WriteLine(welcome); // Output: Hello World
❓ Interview Q&A
Q1: What exactly is a string in .NET?
A: It’s an object of type System.String that stores a sequence of characters and supports Unicode.
Q2: Are strings in .NET mutable?
A: No, they are immutable. Modifying them creates a new object.
Q3: How do you access an individual character in a string?
A: By its zero-based index, e.g., str[2].
Q4: Can strings hold Unicode symbols or emojis?
A: Yes, .NET strings use UTF-16 encoding to support worldwide text, including emojis.
Q5: What namespace and type do .NET strings belong to?
A: System.String in the System namespace.
Q6: How can you check if a string is null or empty?
A: Use string.IsNullOrEmpty() method.
Q7: What is the difference between String and StringBuilder in .NET?
A: String is immutable, while StringBuilder allows efficient modifications.
Q8: How do you concatenate two strings?
A: Using the + operator or string.Concat() method.
Q9: How do you get the length of a string?
A: Using the Length property, e.g., str.Length.
Q10: How can you compare two strings for equality in .NET?
A: Using string.Equals() or the == operator.
📝 MCQs
Q1. What is the starting index of a .NET string?
- 1
- 0
- -1
- Depends
Q2. Can .NET strings be changed directly?
- Yes
- No, they're immutable
- Only with unsafe code
- Sometimes
Q3. Which encoding do .NET strings use?
- UTF-8
- UTF-16
- ASCII
- ISO-8859-1
Q4. Which class represents strings in .NET?
- StringType
- CharArray
- System.String
- Text.String
Q5. Which method checks if a string is empty or null?
- IsEmpty()
- IsNull()
- string.IsNullOrEmpty()
- Length == 0
Q6. How do you get the length of a string?
- Count()
- Size()
- Length property
- GetLength()
Q7. What happens when you modify a string in .NET?
- Original string changes
- Error thrown
- A new string object is created
- Memory is overwritten
Q8. Which method concatenates two strings?
- string.Merge()
- string.Add()
- string.Concat()
- string.Join()
Q9. What is the difference between String and StringBuilder?
- String is mutable
- StringBuilder is immutable
- StringBuilder allows modification
- No difference
Q10. How can you compare two strings ignoring case?
- == operator
- Equals()
- string.Equals(a, b, StringComparison.OrdinalIgnoreCase)
- Compare()
💡 Bonus Insight
For high-performance text building or repeated concatenations, prefer StringBuilder—it avoids memory overhead from creating many new string objects.
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