Func delegate type in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a Func delegate that takes two integers and returns an integer.

C Sharp (C#)

Func<int, int, [1]> add = (x, y) => x + y;

Drag options to blanks, or click blank then click option'

Aint

Bvoid

Cstring

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using void as return type in Func (Func must return a value).

Using string or bool as return type when adding integers.

The Func delegate's last type parameter specifies the return type. Here, it returns an int.

2fill in blank

medium

Complete the code to declare a Func delegate that takes a string and returns its length.

C Sharp (C#)

Func<string, [1]> getLength = s => s.Length;

Drag options to blanks, or click blank then click option'

Aint

Bstring

Cbool

Ddouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using string as return type instead of int.

Using bool or double which do not match Length property type.

The Func delegate returns the length of the string, which is an int.

3fill in blank

hard

Fix the error in the Func delegate declaration to correctly return a boolean indicating if a number is even.

C Sharp (C#)

Func<int, [1]> isEven = n => n % 2 == 0;

Drag options to blanks, or click blank then click option'

Astring

Bbool

Cint

Dvoid

Attempts:

3 left

💡 Hint

Common Mistakes

Using int as return type when the lambda returns a boolean.

Using void which is invalid for Func delegates.

The lambda returns a boolean value, so the Func delegate must have bool as the return type.

4fill in blank

hard

Fill both blanks to declare a Func delegate that takes a double and an int, and returns a double result.

C Sharp (C#)

Func<[1], [2], double> multiply = (a, b) => a * b;

Drag options to blanks, or click blank then click option'

Adouble

Bint

Cstring

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping input types or using string/bool as input types.

Using int as first input when it should be double.

The Func delegate takes a double and an int as inputs and returns a double.

5fill in blank

hard

Fill all three blanks to declare a Func delegate that takes two strings and returns a boolean indicating if they are equal.

C Sharp (C#)

Func<[1], [2], [3]> areEqual = (s1, s2) => s1 == s2;

Drag options to blanks, or click blank then click option'

Astring

Bint

Cbool

Ddouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using int or double as input types instead of string.

Using int or string as return type instead of bool.

The Func delegate takes two string inputs and returns a bool indicating equality.

Practice

1. What is the main purpose of the Func delegate type in C#?

easy

A. To store methods that return a value

B. To store methods that do not return a value

C. To create variables of any data type

D. To define classes

Solution

1. Step 1: Understand what Func represents

   Func is a delegate type designed to hold references to methods that return a value.

2. Step 2: Differentiate from other delegates

   Unlike Action, which stores methods without return values, Func always returns a value.

3. Final Answer:

   To store methods that return a value -> Option A

4. Quick Check:

   Func stores methods with return values = C [OK]

Hint: Remember: Func always returns a value, Action does not [OK]

Common Mistakes:

• Confusing Func with Action delegate
• Thinking Func can store void methods
• Assuming Func defines classes

2. Which of the following is the correct syntax to declare a Func delegate that takes two integers and returns an integer?

easy

A. Func add = (x, y) => x + y;

B. Func add = (x, y) => x + y;

C. Func<int> add = (x, y) => x + y;

D. Func add = (x, y) => x + y;

Solution

1. Step 1: Understand Func generic parameters

   The last type parameter is the return type; previous ones are input types. For two integers input and one integer output, use Func.

2. Step 2: Check lambda expression matches parameters

   The lambda (x, y) => x + y takes two inputs and returns their sum, matching the delegate.

3. Final Answer:

   Func<int, int, int> add = (x, y) => x + y; -> Option B

4. Quick Check:

   Two inputs + one output = Func<int, int, int> [OK]

Hint: Count inputs, last type is output in Func<> [OK]

Common Mistakes:

• Using wrong number of generic parameters
• Mixing input and output types order
• Incorrect lambda parameter count

3. What is the output of the following code?

Func<int, int, int> multiply = (a, b) => a * b;
int result = multiply(3, 4);
Console.WriteLine(result);

medium

A. 12

B. 7

C. 34

D. Error

Solution

1. Step 1: Understand the Func delegate and lambda

   The delegate multiply takes two integers and returns their product.

2. Step 2: Calculate the result of multiply(3, 4)

   3 multiplied by 4 equals 12.

3. Final Answer:

   12 -> Option A

4. Quick Check:

   3 * 4 = 12 [OK]

Hint: Multiply inputs as lambda defines [OK]

Common Mistakes:

• Adding instead of multiplying
• Concatenating numbers as strings
• Expecting syntax error

4. Identify the error in this code snippet:

Func<int, int> square = x => x * x;
int result = square(5, 2);
Console.WriteLine(result);

medium

A. Syntax error in lambda expression

B. Missing return statement in lambda

C. Incorrect delegate type for lambda

D. Too many arguments passed to the Func delegate

Solution

1. Step 1: Check Func delegate signature

   Func<int, int> expects one integer input and returns an integer.

2. Step 2: Check method call arguments

   The call square(5, 2) passes two arguments, but the delegate expects only one.

3. Final Answer:

   Too many arguments passed to the Func delegate -> Option D

4. Quick Check:

   One input expected, two given = error [OK]

Hint: Match argument count to Func input count [OK]

Common Mistakes:

• Passing wrong number of arguments
• Confusing input and output types
• Assuming lambda needs explicit return

5. You want to create a Func delegate that takes a string and returns its length only if the string is not null or empty; otherwise, it returns zero. Which of the following implementations correctly achieves this?

hard

A. Func lengthFunc = s => { if (s == null) return 0; else return s.Length; };

B. Func lengthFunc = s => s.Length;

C. Func lengthFunc = s => string.IsNullOrEmpty(s) ? 0 : s.Length;

D. Func lengthFunc = s => s == "" ? s.Length : 0;

Solution

1. Step 1: Understand the requirement

   The function must return 0 if the string is null or empty, else return its length.

2. Step 2: Analyze each option

   Func lengthFunc = s => string.IsNullOrEmpty(s) ? 0 : s.Length; uses string.IsNullOrEmpty to check both conditions and returns 0 or length accordingly, which is correct. Func lengthFunc = s => s.Length; does not check for null or empty and may throw an error. Func lengthFunc = s => { if (s == null) return 0; else return s.Length; }; checks only for null, not empty. Func lengthFunc = s => s == "" ? s.Length : 0; returns length only if string is empty, which is opposite.

3. Final Answer:

   Func<string, int> lengthFunc = s => string.IsNullOrEmpty(s) ? 0 : s.Length; -> Option C

4. Quick Check:

   Check null or empty with IsNullOrEmpty = Func lengthFunc = s => string.IsNullOrEmpty(s) ? 0 : s.Length; [OK]

Hint: Use string.IsNullOrEmpty to check safely [OK]

Common Mistakes:

• Not checking empty string
• Only checking null but not empty
• Returning wrong value for empty string