C# Programming - MCQ Practice Questions

C# uses the syntax 'type variableName = value;' to declare and initialize variables. The equals sign (=) is the assignment operator.

C# is case-sensitive. The lowercase keyword 'class' is used to define a class. 'Class' and 'CLASS' are not valid keywords.

++x is pre-increment. It increments x first (x becomes 6), then assigns the value to y. So both x and y are 6.

int is a value type (primitive type). string, object, and arrays are reference types in C#.

The 'const' keyword is used to declare constants in C#. 'final' is Java syntax. While 'readonly' can be used, 'const' is the proper keyword for compile-time constants.

Console class is part of the System namespace. You need to include 'using System;' at the beginning of your code to use Console.WriteLine().

For strings, '==' compares references (memory addresses) while Equals() compares the actual string values. However, C# has optimized string comparison, so both often behave similarly for string literals.

int.Parse() converts a string to an integer. Direct casting doesn't work for strings. Convert.ToInt32() would throw an exception if the string is not a valid number. The 'as' operator doesn't work for strings to primitives.

Variable names in C# can contain letters, digits, and underscores. They cannot contain special characters like '$'. The variable name must start with a letter or underscore.

String concatenation using '+' operator joins the two strings. s becomes 'Hello World' after the concatenation.

In C#, 'int?' is used to declare a nullable integer. A regular 'int' cannot be assigned null. int* is a pointer (unsafe code), not a nullable type.

(5 > 3) is true, but (2 < 1) is false. The '&&' (AND) operator returns true only if both conditions are true. Since one is false, the result is false.

'sealed' keyword prevents a class from being inherited in C#. 'final' is Java syntax. 'abstract' requires a class to be inherited. 'static' makes members class-level, not related to inheritance.

Accessing an array element beyond its bounds throws an IndexOutOfRangeException at runtime. This is a safety feature to prevent accessing invalid memory.

x++ returns 10 then increments x to 11. ++y increments y to 21 then returns 21. z = 10 + 21 = 31. Final output: 11 21 31

In C#, structs are value types (stored on stack) while classes are reference types (stored on heap). This is a fundamental difference between the two.

Enum is a value type in C#. String, Interface, and Delegate are reference types.

The default access modifier for class members in C# is private, meaning they are accessible only within the same class.

Only nullable types (using ?) can hold null values for value types. int? is a nullable integer that can hold null.

Integer division in C# truncates the decimal part. $\frac{10}{3}$ = 3 (not 3.33) because both operands are integers.