Indexer with custom types in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an indexer in the class.

C Sharp (C#)

public string this[[1] index] { get { return "Value" + index; } }

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

Aint

Bstring

Cdouble

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of int for the index parameter.

Forgetting to specify the parameter type.

The indexer uses an int parameter to access elements by integer index.

2fill in blank

medium

Complete the code to define a custom type used as an indexer parameter.

C Sharp (C#)

public struct [1] { public int Id; }

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

AIndex

BKey

CItem

DValue

Attempts:

3 left

💡 Hint

Common Mistakes

Using a class instead of a struct.

Using a generic or unrelated name.

The struct Key is used as a custom type for the indexer parameter.

3fill in blank

hard

Fix the error in the indexer declaration using the custom type.

C Sharp (C#)

public string this[[1] key] { get { return "Value" + key.Id; } }

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

AKey

Bint

Cstring

Dobject

Attempts:

3 left

💡 Hint

Common Mistakes

Using int or string instead of the custom type.

Using object which does not have the Id property.

The indexer parameter must be of the custom type Key to access its Id property.

4fill in blank

hard

Fill both blanks to complete the indexer with get and set accessors using the custom type.

C Sharp (C#)

private Dictionary<[1], string> data = new Dictionary<[2], string>();
public string this[Key key] {
    get => data[key];
    set => data[key] = value;
}

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

AKey

Bint

Cstring

Dobject

Attempts:

3 left

💡 Hint

Common Mistakes

Using different types for the dictionary keys.

Using primitive types instead of the custom type.

The dictionary uses the custom type Key as its key type, so both blanks must be Key.

5fill in blank

hard

Fill all three blanks to complete the indexer that checks if the key exists before returning a value or default.

C Sharp (C#)

public string this[[1] key] {
    get {
        if (data.[2](key))
            return data[key];
        else
            return [3];
    }
}

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

AKey

BContainsKey

Cnull

DTryGetValue

Attempts:

3 left

💡 Hint

Common Mistakes

Using TryGetValue incorrectly.

Returning an empty string instead of null.

Using wrong parameter type.

The indexer uses Key as parameter type, checks existence with ContainsKey, and returns null if not found.