A generic collection storing key-value pairs.

What is a Dictionary<TKey, TValue>? | FullStackPrep.Dev

💡 Concept: Dictionary<TKey, TValue> in C#

Dictionary<TKey, TValue> is a generic collection that stores key-value pairs with fast lookup based on keys.

📘 Quick Intro

The Dictionary provides an efficient way to map keys to values, useful for caching, lookup tables, and fast retrieval.

🧠 Analogy

Think of a Dictionary as a real-world dictionary where a word (key) maps to its definition (value).

🔧 Technical Explanation

🔑 Keys are unique; values can be duplicated.
⚙️ Uses hashing for fast key-based retrieval.
📚 Part of System.Collections.Generic namespace.
🛠️ Supports adding, removing, and searching key-value pairs.
💡 Offers better performance than non-generic Hashtable.

🎯 Use Cases

✅ Lookup tables.
✅ Caching data with keys.
✅ Storing configuration settings.
✅ Implementing dictionaries and maps.

💻 Code Example


using System;
using System.Collections.Generic;

class Program {
    static void Main() {
        Dictionary<string, int> ages = new Dictionary<string, int>();
        ages["Alice"] = 30;
        ages["Bob"] = 25;

        foreach (var kvp in ages) {
            Console.WriteLine($""{kvp.Key}: {kvp.Value}"");
        }
    }
}

❓ Interview Q&A

Q1: What is Dictionary<TKey, TValue>?
A: A collection of key-value pairs.

Q2: Can keys be duplicated?
A: No, keys must be unique.

Q3: What is hashing?
A: A technique for fast data retrieval.

Q4: What namespace contains Dictionary?
A: System.Collections.Generic.

Q5: How to add items?
A: Use Add or indexer.

Q6: Can values be duplicated?
A: Yes.

Q7: How to check if a key exists?
A: Use ContainsKey method.

Q8: How to remove items?
A: Use Remove method.

Q9: Is Dictionary thread-safe?
A: No, synchronization needed.

Q10: Can Dictionary be serialized?
A: Yes.

📝 MCQs

Q1. What is Dictionary<TKey, TValue>?

List
Key-value pair collection
Array
Queue

Q2. Can keys be duplicated?

Yes
No
Maybe
Sometimes

Q3. What is hashing?

Slow data retrieval
Fast data retrieval
Sorting
Searching

Q4. Namespace for Dictionary?

System.IO
System.Collections.Generic
System.Text
System.Threading

Q5. How to add items?

Remove
Add or indexer
Clear
Update

Q6. Can values be duplicated?

No
Yes
Sometimes
Never

Q7. How to check key existence?

ContainsValue
ContainsKey
Exists
HasKey

Q8. How to remove items?

Delete
Remove method
Clear
Dispose

Q9. Is Dictionary thread-safe?

Yes
No
Sometimes
Always

Q10. Can Dictionary be serialized?

No
Yes
Sometimes
Never

💡 Bonus Insight

Dictionary is highly efficient for key-based lookups, making it a go-to collection for many scenarios.

📄 PDF Download

Need a handy summary for your notes? Download this topic as a PDF!

📄 PDF Download Coming Soon

What is a Dictionary<TKey, TValue>?