Dictionary methods and access patterns in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of accessing dictionary with TryGetValue

What is the output of this C# code snippet?

C Sharp (C#)

var dict = new Dictionary<string, int> { {"apple", 3}, {"banana", 5} };
if (dict.TryGetValue("banana", out int value))
{
    Console.WriteLine(value);
}
else
{
    Console.WriteLine("Not found");
}

A 5

B Runtime error

C 3

D Not found

💡 Hint

TryGetValue returns true if the key exists and outputs the value.

The key "banana" exists with value 5, so TryGetValue returns true and prints 5.

❓ Predict Output

intermediate

Result of removing a key from dictionary

What is the output of this C# code?

C Sharp (C#)

var dict = new Dictionary<int, string> { {1, "one"}, {2, "two"} };
bool removed = dict.Remove(3);
Console.WriteLine(removed);

A False

B True

C KeyNotFoundException

D Compilation error

💡 Hint

Remove returns false if the key does not exist.

Key 3 does not exist, so Remove returns false and prints False.

❓ Predict Output

advanced

Output of dictionary indexer with missing key

What happens when this C# code runs?

C Sharp (C#)

var dict = new Dictionary<string, int> { {"x", 10} };
Console.WriteLine(dict["y"]);

A 0

B KeyNotFoundException

C null

D Compilation error

💡 Hint

Accessing a missing key with indexer throws an exception.

The key "y" does not exist, so accessing dict["y"] throws KeyNotFoundException.

❓ Predict Output

advanced

Count of items after TryAdd calls

What is the count of items in the dictionary after this code runs?

C Sharp (C#)

var dict = new Dictionary<int, string>();
dict.TryAdd(1, "one");
dict.TryAdd(1, "uno");
dict.TryAdd(2, "two");
Console.WriteLine(dict.Count);

A 3

B 1

C 2

D Runtime error

💡 Hint

TryAdd does not overwrite existing keys.

The second TryAdd with key 1 fails, so only keys 1 and 2 exist, count is 2.

❓ Predict Output

expert

Output of iterating dictionary keys and values

What is the output of this C# code?

C Sharp (C#)

var dict = new Dictionary<string, int> { {"a", 1}, {"b", 2} };
foreach (var key in dict.Keys)
{
    Console.Write(key);
}
foreach (var value in dict.Values)
{
    Console.Write(value);
}

A b2a1

B 12ab

C a1b2

D ab12

💡 Hint

Keys and values are iterated in the same order as insertion.

Keys are "a", "b" and values are 1, 2, so output is "ab12".