C# DataType MCQs

Question 21: What will be the output of the following program?

public static void Main(string[] args)
{
	object o = "Bill";
		
	Console.WriteLine(o.GetType());
}

Answer: B

The type of object depends on the assigned value's type. If it is a string, then it will be of string type, and if it is int, then it will be of int type. Here string is assigned to an object o, so the type will be of string type.

Question 22: What will be the output of the following program?

public static void Main(string[] args)
{
	object o = "Bill";
	Change(o);
}
static void Change(object obj)
{ 
	Console.Write("object");
}
	
static void Change(string str)
{ 
	Console.Write("string");
}

Answer: A.

Above, the method gets called based on the type of variable passed. The type of o is declared as object, so it will call the Change(Object obj) method whose parameter type is an object. If you pass the string type variable, then it will call the Change(string str) method. Note it calls an overloaded method based on the type of a variable declared, not on the type of a value assigned.

Question 23: What will be the output of the following program?

public static void Main(string[] args)
{
	int i=10;
	float f = 34.412F;
	display(i);
	display(f);
}

static void display(float f){
	Console.Write(f + " ");
}

Answer: C.

An int is converted to float implicitly. However, the float cannot be converted to int implicitly. Above, when an int is passed in the display(float f) method, it gets converted into float implicitly.

Learn C# number types.

Question 24: What will be the output of the following program?

public static void Main(string[] args)
{
	int i=10;
	float f = 34.412F;
	display(i);
	display(f);
}

static void display(int i){
	Console.Write(i + " ");
}

Answer: A.

The float value cannot be converted implicitly, so the above program will give a compile-time error because it cannot find the display() method with float parameter for display(f). You must convert float to int explicitly.

float x = 10.5F;
int y = (int)x;
Console.WriteLine(y);

Question 25: Which of the following convert a string to an int?

Answer: A, B, C, D

In C#, string to int can be converted explicitly, using Convert.ToInt32() method, using int.Parse() method, and using int.TryParse() method.