Zip operation in C Sharp (C#) - Mini Project: Build & Apply

Zip Operation in C#

📖 Scenario: You work in a small store. You have two lists: one with product names and one with their prices. You want to combine these lists to see each product with its price.

🎯 Goal: Build a program that uses the Zip operation to pair each product with its price and print the pairs.

📋 What You'll Learn

Create two lists: one called products with exact values "Apple", "Banana", "Cherry"

Create another list called prices with exact values 1.2, 0.5, 2.0

Use a variable called productPrices to store the zipped pairs

Use a foreach loop with variables product and price to iterate over productPrices

Print each product and price in the format: "Apple: $1.2"

💡 Why This Matters

🌍 Real World

Stores and shops often have separate lists for products and prices. Combining them helps show clear price tags or receipts.

💼 Career

Knowing how to combine related data from different lists is useful in many programming jobs, especially in data processing and user interface development.

1

Create the product and price lists

Create a list of strings called products with these exact values: "Apple", "Banana", "Cherry". Also create a list of doubles called prices with these exact values: 1.2, 0.5, 2.0.

C Sharp (C#)

// Create the list called products with "Apple", "Banana", "Cherry"
// Create the list called prices with 1.2, 0.5, 2.0

Hint

Use List<string> for products and List<double> for prices. Initialize them with the exact values.

2

Create the zipped pairs

Create a variable called productPrices that uses products.Zip(prices, (product, price) => (product, price)) to combine the two lists into pairs.

C Sharp (C#)

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        List products = new List { "Apple", "Banana", "Cherry" };
        List prices = new List { 1.2, 0.5, 2.0 };

        // Create productPrices by zipping products and prices
        // Your code here
    }
}

Hint

Use var productPrices = products.Zip(prices, (product, price) => (product, price)); to combine the lists.

3

Loop through the zipped pairs

Use a foreach loop with variables product and price to iterate over productPrices.

C Sharp (C#)

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        List products = new List { "Apple", "Banana", "Cherry" };
        List prices = new List { 1.2, 0.5, 2.0 };

        var productPrices = products.Zip(prices, (product, price) => (product, price));

        // Use foreach with product and price to loop over productPrices
        // Your code here
    }
}

Hint

Use foreach (var (product, price) in productPrices) to loop through the pairs.

4

Print each product with its price

Inside the foreach loop, write Console.WriteLine($"{product}: ${price}"); to print each product and its price.

C Sharp (C#)

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        List products = new List { "Apple", "Banana", "Cherry" };
        List prices = new List { 1.2, 0.5, 2.0 };

        var productPrices = products.Zip(prices, (product, price) => (product, price));

        foreach (var (product, price) in productPrices)
        {
            // Print product and price here
            // Your code here
        }
    }
}

Hint

Use Console.WriteLine($"{product}: ${price}"); inside the loop to print each pair.

Practice

1.

What does the Zip method do in C#?

Choose the best description.

easy

A. Combines all elements from two collections into one long list.

B. Sorts elements in a collection in ascending order.

C. Filters elements from a collection based on a condition.

D. Pairs elements from two collections one by one until the shorter ends.

Solution

1. Step 1: Understand the purpose of Zip

   The Zip method pairs elements from two collections by their positions.

2. Step 2: Recognize stopping condition

   It stops when the shorter collection runs out of elements, so no extra elements are included.

3. Final Answer:

   Pairs elements from two collections one by one until the shorter ends. -> Option D

4. Quick Check:

   Zip pairs elements until the shorter ends = B [OK]

Hint: Zip pairs elements until shortest collection ends [OK]

Common Mistakes:

• Thinking Zip combines all elements regardless of length
• Confusing Zip with filtering or sorting
• Assuming Zip merges collections end-to-end

2.

Which of the following is the correct syntax to use Zip on two lists list1 and list2 to sum their elements?

var result = list1.Zip(list2, (a, b) => ? );

easy

A. a + b

B. a - b

C. a * b

D. a / b

Solution

1. Step 1: Identify the operation to sum elements

   The lambda expression should add the two elements: a + b.

2. Step 2: Confirm syntax correctness

   The syntax list1.Zip(list2, (a, b) => a + b) correctly sums paired elements.

3. Final Answer:

   a + b -> Option A

4. Quick Check:

   Sum elements with Zip = a + b [OK]

Hint: Use (a, b) => a + b to sum zipped elements [OK]

Common Mistakes:

• Using wrong operator like - or * instead of +
• Forgetting lambda syntax
• Mixing parameter order

3.

What is the output of this C# code?

var numbers = new[] {1, 2, 3};
var words = new[] {"one", "two"};
var zipped = numbers.Zip(words, (n, w) => $"{n}:{w}");
foreach(var item in zipped) Console.Write(item + " ");

medium

A. 1:one 2:two 3:

B. one:1 two:2

C. 1:one 2:two

D. 1:one 2:two 3:three

Solution

1. Step 1: Check lengths of arrays

   numbers has 3 elements, words has 2 elements; Zip stops at shorter length (2).

2. Step 2: Pair elements and format output

   Pairs: (1, "one"), (2, "two"); output strings: "1:one", "2:two".

3. Final Answer:

   1:one 2:two -> Option C

4. Quick Check:

   Zip stops at shorter list = C [OK]

Hint: Zip stops at shorter list length, so output matches shortest [OK]

Common Mistakes:

• Expecting output for all elements of longer list
• Mixing order of elements in output
• Adding extra spaces or elements

4.

Identify the error in this code snippet using Zip:

var a = new[] {1, 2, 3};
var b = new[] {4, 5};
var result = a.Zip(b, (x, y) => x + y).ToList();
Console.WriteLine(result[2]);

medium

A. Syntax error in Zip lambda expression

B. Index out of range exception at result[2]

C. Null reference exception

D. No error, prints 7

Solution

1. Step 1: Understand Zip output length

   Zip stops at shorter array length, so result has 2 elements only.

2. Step 2: Accessing invalid index

   Accessing result[2] (third element) causes IndexOutOfRangeException.

3. Final Answer:

   Index out of range exception at result[2] -> Option B

4. Quick Check:

   Accessing beyond Zip length causes error = A [OK]

Hint: Zip result length = shorter input length; check indexes [OK]

Common Mistakes:

• Assuming Zip output length equals longer list
• Ignoring zero-based indexing
• Confusing syntax errors with runtime errors

5.

You have two lists:

var keys = new[] {"a", "b", "c", "d"};
var values = new[] {1, 2, 3};

Using Zip, how can you create a dictionary that pairs keys and values only for matching positions?

hard

A. keys.Zip(values, (k, v) => new {k, v}).ToDictionary(x => x.k, x => x.v)

B. keys.Select((k, i) => new {k, v = values[i]}).ToDictionary(x => x.k, x => x.v)

C. keys.Concat(values).ToDictionary(k => k, v => v)

D. values.Zip(keys, (k, v) => new {k, v}).ToDictionary(x => x.k, x => x.v)

Solution

1. Step 1: Use Zip to pair keys and values

   Zip pairs elements by position, stopping at shorter list length (3 pairs).

2. Step 2: Convert pairs to dictionary

   Create anonymous objects with key and value, then call ToDictionary with key and value selectors.

3. Final Answer:

   keys.Zip(values, (k, v) => new {k, v}).ToDictionary(x => x.k, x => x.v) -> Option A

4. Quick Check:

   Zip pairs + ToDictionary = A [OK]

Hint: Zip keys and values, then ToDictionary with selectors [OK]

Common Mistakes:

• Using Concat instead of Zip
• Reversing keys and values in Zip
• Using Select without bounds check causing errors