Object type as universal base in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Object type as universal base

Create variable of type object

↓

Assign any value (int, string, etc.)

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Use variable as universal container

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Cast back to original type when needed

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Use value

In C#, the object type can hold any data type because all types inherit from it. You store any value in an object variable and cast it back when needed.

Execution Sample

C Sharp (C#)

object obj = 42;
Console.WriteLine(obj);
obj = "hello";
Console.WriteLine(obj);
int num = (int)obj; // causes error

This code stores an int and then a string in an object variable, then tries to cast back to int (which fails).

Execution Table

Step	Code Line	Variable	Value	Action	Notes
1	object obj = 42;	obj	42 (int)	Assign int 42 to obj	Boxing int into object
2	Console.WriteLine(obj);	obj	42 (int)	Print obj	Outputs 42
3	obj = "hello";	obj	"hello" (string)	Assign string to obj	obj now holds string
4	Console.WriteLine(obj);	obj	"hello" (string)	Print obj	Outputs hello
5	int num = (int)obj;	obj	"hello" (string)	Cast obj to int	Invalid cast exception at runtime

💡 Execution stops at step 5 due to invalid cast from string to int.

Variable Tracker

Variable	Start	After Step 1	After Step 3	After Step 5 (error)
obj	null	42 (int)	"hello" (string)	Exception thrown, no value
num	undefined	undefined	undefined	undefined (not assigned due to error)

Key Moments - 2 Insights

Why does casting obj to int fail at step 5?

Because obj currently holds a string "hello", not an int. Casting requires the actual stored type to match, as shown in execution_table row 5.

Can obj hold any type of value?

Yes, obj is of type object, the universal base type in C#. It can hold any value type or reference type, as shown in steps 1 and 3.

Visual Quiz - 3 Questions

Look at the execution_table at step 3. What type of value does obj hold?

A int 42

B object null

C string "hello"

D int 0

💡 Hint

Check the 'Value' column in execution_table row 3.

At which step does the program throw an error?

A Step 2

B Step 5

C Step 4

D Step 1

💡 Hint

Look at the 'Notes' column for the step where casting fails.

If we assign obj = 100; then cast to int, what would happen?

A Casting succeeds and num = 100

B Casting fails with exception

C num becomes null

D Compilation error

💡 Hint

Refer to how boxing/unboxing works in variable_tracker and execution_table step 1.

Concept Snapshot

object is the universal base type in C#
It can hold any value or reference type
Assigning value types boxes them into object
Casting back requires correct original type
Invalid cast causes runtime exception
Use object to store mixed types carefully

Full Transcript

In C#, the object type is the universal base type. This means any value or reference type can be stored in a variable of type object. When you assign a value type like int to an object, it is boxed, meaning wrapped inside an object container. You can then assign a different type like string to the same object variable. However, when you want to get the original value back, you must cast the object to the correct type. If you cast to the wrong type, like casting a string to int, the program throws an invalid cast exception at runtime. This example shows storing 42 (int) in obj, printing it, then storing "hello" (string), printing it, and finally trying to cast back to int which fails. This teaches that object is flexible but requires careful casting.