Why strong typing matters in C# - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a strongly typed integer variable in C#.

C Sharp (C#)

int number = [1];

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

Atrue

B"10"

C10

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning a string value like "10" to an int variable.

Using true or null which are not integers.

In C#, int variables must be assigned integer values like 10. Assigning a string or other types causes errors.

2fill in blank

medium

Complete the code to declare a strongly typed string variable in C#.

C Sharp (C#)

string greeting = [1];

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

A100

Bnull

Ctrue

D"Hello"

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning numbers or booleans to a string variable without quotes.

Forgetting the quotes around the text.

Strings in C# must be enclosed in double quotes. So "Hello" is correct.

3fill in blank

hard

Fix the error in the code by choosing the correct type for the variable.

C Sharp (C#)

var isActive = [1];

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

Anull

Btrue

C1

D"true"

Attempts:

3 left

💡 Hint

Common Mistakes

Using "true" as a string instead of boolean true.

Using numbers like 1 instead of boolean values.

The variable isActive should be a boolean. The value true without quotes is the correct boolean literal.

4fill in blank

hard

Fill both blanks to create a strongly typed list of integers and add a number to it.

C Sharp (C#)

List<int> numbers = new [1]();
numbers.[2](5);

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

AList<int>

BAdd

CAddRange

DArrayList

Attempts:

3 left

💡 Hint

Common Mistakes

Using ArrayList which is not strongly typed.

Using AddRange which expects a collection, not a single item.

We create a new List<int> and use the Add method to add a single integer.

5fill in blank

hard

Fill all three blanks to declare a strongly typed dictionary and add a key-value pair.

C Sharp (C#)

Dictionary<[1], [2]> capitals = new Dictionary<[3], string>();
capitals.Add("France", "Paris");

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

Astring

Bint

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using int or bool for keys or values incorrectly.

Mismatching types between declaration and constructor.

The dictionary uses string as the key type and string as the value type. So both key and value types are string.

Practice

1. What does strong typing in C# mean?

easy

A. Each variable has a fixed data type that cannot change

B. Variables can change their type during runtime

C. Types are checked only when the program runs

D. Variables do not need a type declaration

Solution

1. Step 1: Understand the meaning of strong typing

   Strong typing means variables have a fixed type assigned at declaration.

2. Step 2: Compare options with this definition

   Only 'Each variable has a fixed data type that cannot change' matches this definition.

3. Final Answer:

   Each variable has a fixed data type that cannot change -> Option A

4. Quick Check:

   Strong typing = fixed variable types [OK]

Hint: Strong typing means fixed variable types from start [OK]

Common Mistakes:

• Thinking variables can change type anytime
• Confusing strong typing with dynamic typing
• Believing types are checked only at runtime

2. Which of the following is the correct way to declare an integer variable in C# with strong typing?

easy

A. int number;

B. var number = "ten";

C. number = 10;

D. int number = 10;

Solution

1. Step 1: Identify correct syntax for typed variable declaration

   In C#, declaring an int variable requires specifying type and optionally initializing it.

2. Step 2: Check each option

   int number = 10; declares an int variable with initialization correctly. var number = "ten"; uses var with a string, not int. number = 10; misses type declaration. int number; declares but does not initialize, which is allowed but less complete.

3. Final Answer:

   int number = 10; -> Option D

4. Quick Check:

   Typed declaration with initialization = int number = 10; [OK]

Hint: Declare type before variable name for strong typing [OK]

Common Mistakes:

• Omitting the type before variable name
• Using var with incompatible types
• Not initializing variables when required

3. What will be the output of this C# code?

int x = 5;
string y = "5";
Console.WriteLine(x == y);

medium

A. Compilation error

B. False

C. Runtime exception

D. True

Solution

1. Step 1: Analyze the comparison between int and string

   The code tries to compare an int variable 'x' with a string variable 'y' using '=='. C# is strongly typed and does not allow direct comparison between int and string.

2. Step 2: Understand C# compiler behavior

   This mismatch causes a compilation error because types are incompatible for '==' operator without conversion.

3. Final Answer:

   Compilation error -> Option A

4. Quick Check:

   Strong typing prevents int == string comparison [OK]

Hint: Different types can't be compared directly in C# [OK]

Common Mistakes:

• Assuming int and string can be compared directly
• Expecting output True or False without error
• Ignoring type mismatch errors

4. Identify the error in this C# code snippet:

double price = 19.99;
int quantity = "5";
double total = price * quantity;
Console.WriteLine(total);

medium

A. Cannot multiply double and int

B. Cannot assign string to int variable

C. Missing semicolon after quantity declaration

D. Console.WriteLine syntax is incorrect

Solution

1. Step 1: Check variable assignments

   The variable 'quantity' is declared as int but assigned a string "5", which is invalid in strong typing.

2. Step 2: Verify other operations

   Multiplying double and int is allowed, semicolons are present, and Console.WriteLine syntax is correct.

3. Final Answer:

   Cannot assign string to int variable -> Option B

4. Quick Check:

   Strong typing forbids assigning string to int [OK]

Hint: Check variable types match assigned values [OK]

Common Mistakes:

• Thinking double and int cannot be multiplied
• Ignoring type mismatch in assignment
• Assuming missing semicolon causes error

5. You want to create a method in C# that accepts only integers and returns their square. Which strong typing feature helps prevent passing wrong types and why?

hard

A. Casting parameters inside the method fixes wrong types

B. Using var keyword allows any type to be passed safely

C. Method parameter type declaration ensures only integers are accepted

D. Omitting types in method signature makes it flexible

Solution

1. Step 1: Understand method parameter typing in C#

   Strong typing requires method parameters to declare their types, so only matching types can be passed.

2. Step 2: Evaluate options for type safety

   'Method parameter type declaration ensures only integers are accepted' correctly states that parameter type declaration enforces integer input. The other options either allow unsafe types or rely on runtime casting, which is error-prone.

3. Final Answer:

   Method parameter type declaration ensures only integers are accepted -> Option C

4. Quick Check:

   Parameter types enforce input types in strong typing [OK]

Hint: Declare parameter types to restrict input [OK]

Common Mistakes:

• Thinking var allows safe type enforcement
• Relying on casting instead of type declaration
• Omitting types for flexibility causes errors