Optional parameters in C Sharp (C#) - Cheat Sheet & Quick Revision

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beginner

What are optional parameters in C#?

Optional parameters are method parameters that have a default value. When calling the method, you can skip these parameters, and the default value will be used.

beginner

How do you declare an optional parameter in C#?

You declare an optional parameter by assigning it a default value in the method signature, for example:

void Greet(string name = "Guest")

intermediate

Can optional parameters be placed anywhere in the parameter list?

No. Optional parameters must come after all required parameters in the method signature.

beginner

What happens if you call a method without providing an optional parameter?

The method uses the default value specified for that optional parameter.

beginner

Example: What is the output of this code?<br>

void PrintMessage(string message = "Hello") { Console.WriteLine(message); }<br>PrintMessage();

The output is:<br>

Hello

<br>Because the method was called without an argument, so the default value "Hello" is used.

How do you specify an optional parameter in C#?

A By placing the parameter inside square brackets

B By assigning a default value in the method signature

C By marking the parameter with the keyword 'optional'

D By declaring the parameter as 'null'

Optional parameters are declared by assigning them a default value in the method signature.

Where must optional parameters be placed in the parameter list?

A After all required parameters

B Anywhere in the list

C Only as the first parameter

D Before required parameters

Optional parameters must come after all required parameters in the method signature.

What happens if you call a method without providing an optional parameter?

A The default value of the optional parameter is used

B The method throws an error

C The parameter is set to null

D The method ignores the parameter

If an optional parameter is not provided, the method uses its default value.

Which of these is a valid method declaration with an optional parameter?

A void Foo(int x = 5, int y = 10, int z)

B void Foo(int x = 5, int y)

C void Foo(int x, int y)

D void Foo(int x, int y = 10)

Optional parameters must come after required ones, so 'int y = 10' after 'int x' is valid.

Can optional parameters be used with named arguments?

A No, named arguments cannot be used with optional parameters

B Only if all parameters are optional

C Yes, you can skip optional parameters by naming others

D Only in static methods

Named arguments allow you to specify only some parameters, skipping optional ones.

Explain what optional parameters are and how to use them in C# methods.

Think about how you can make some method inputs not required.

Describe the rules about the position of optional parameters in a method's parameter list.

Consider what happens if you put an optional parameter before a required one.