C# MCQ Practice Questions

Which of the following is the correct syntax to define a nullable integer in C#?

• int? x;

• nullable int x;

• int x = null;

• nullable x = new nullable();

What is the default value of a string variable?

• ""

• null

• 0

• undefined

Which keyword is used to define a constant value?

• const

• readonly

• static

• final

Which of the following is NOT a valid C# keyword?

• volatile

• yield

• include

• typeof

What is the size of a bool type in C#?

• 1 bit

• 1 byte

• 4 bytes

• 2 bytes

What is the maximum value of a byte?

• 127

• 255

• 1024

• 65535

Which of the following types can be used with the 'var' keyword?

• Anonymous types

• Value types

• Reference types

• All of the above

Which of the following is NOT a value type?

• int

• double

• bool

• string

Which of the following statements about readonly and const in C# is true?

• Both readonly and const can be assigned at runtime

• readonly can be assigned at runtime, const cannot

• const can be assigned at runtime, readonly cannot

• Both readonly and const cannot be assigned at runtime

Which keyword prevents a variable from being modified after initialization?

• readonly

• const

• static

• Both A & B