Casting with as and is operators in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to cast the object to a string using the 'as' operator.

C Sharp (C#)

object obj = "hello";
string str = obj [1] string;

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

Ato

Bis

Ccast

Das

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'is' instead of 'as' for casting.

Trying to use 'cast' keyword which does not exist.

The 'as' operator attempts to cast an object to a specified type and returns null if it fails.

2fill in blank

medium

Complete the code to check if 'obj' is a string using the 'is' operator.

C Sharp (C#)

object obj = "world";
if (obj [1] string)
{
    Console.WriteLine("It's a string!");
}

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Aas

Bis

C==

Dequals

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'as' instead of 'is' for type checking.

Using '==' which compares references, not types.

The 'is' operator checks if an object is of a certain type and returns a boolean.

3fill in blank

hard

Fix the error in the code by replacing the incorrect cast with the correct 'as' operator.

C Sharp (C#)

object obj = 123;
string str = obj [1] string;
if (str != null)
{
    Console.WriteLine(str);
}

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

Aas

B(string)

Cis

Dto

Attempts:

3 left

💡 Hint

Common Mistakes

Using explicit cast '(string)' which can cause exceptions.

Using 'is' which only checks type but does not cast.

The '(string)' cast throws an exception if the cast fails. Using 'as' returns null instead, which is safer here.

4fill in blank

hard

Fill both blanks to safely cast 'obj' to string and check if the cast succeeded.

C Sharp (C#)

object obj = GetObject();
string str = obj [1] string;
if (str [2] null)
{
    Console.WriteLine(str);
}

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Aas

B==

C!=

Dis

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'is' instead of 'as' for casting.

Checking with '==' null instead of '!=' null.

Use 'as' to cast safely and '!=' to check if the cast was successful (not null).

5fill in blank

hard

Fill all three blanks to check type with 'is', cast with 'as', and verify the cast result.

C Sharp (C#)

object obj = GetObject();
if (obj [1] string)
{
    string str = obj [2] string;
    if (str [3] null)
    {
        Console.WriteLine(str);
    }
}

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

Ais

Bas

C!=

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' null instead of '!=' null.

Using explicit cast instead of 'as'.

First check type with 'is', then cast with 'as', and finally check that the cast result is not null.