Attribute declaration syntax in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an attribute in C#?

An attribute in C# is a way to add metadata to your code, like extra information about classes, methods, or properties that can be used by the compiler or runtime.

beginner

How do you declare an attribute in C#?

You declare an attribute by creating a class that inherits from System.Attribute and usually ends with the word 'Attribute'.

beginner

What is the syntax to apply an attribute to a class or method?

You place the attribute name in square brackets above the class or method. For example: <br><pre>[Serializable]<br>public class MyClass { }</pre>

intermediate

Can attribute names be shortened when applied? How?

Yes. When applying an attribute, you can omit the 'Attribute' suffix. For example, [Serializable] is short for [SerializableAttribute].

intermediate

How do you pass parameters to an attribute?

You pass parameters inside parentheses after the attribute name, like a method call. For example: <br>

[Obsolete("Use new method instead")]
public void OldMethod() { }

Which base class must a custom attribute class inherit from in C#?

A System.Class

B System.Attribute

C System.Metadata

D System.Object

All custom attributes must inherit from System.Attribute to be recognized as attributes.

How do you apply an attribute named 'TestAttribute' to a method named 'Run'?

A Both B and C are correct

B [TestAttribute] public void Run() { }

C [Test] public void Run() { }

D You cannot apply attributes to methods

You can use either [Test] or [TestAttribute] because the 'Attribute' suffix is optional when applying.

What symbol is used to declare an attribute above a class or method?

A {}

B ()

C []

D <>

Attributes are declared using square brackets [] above the target code element.

How do you pass a string parameter 'Hello' to an attribute named 'Example'?

A [Example: "Hello"]

B [Example('Hello')]

C [Example = "Hello"]

D [Example("Hello")]

Parameters are passed inside parentheses using normal method call syntax.

Which of these is a valid attribute class declaration?

A public class MyAttr : System.Attribute { }

B public class MyAttr { }

C public attribute MyAttr { }

D public class MyAttr : AttributeBase { }

Custom attributes must inherit from System.Attribute to be valid.

Explain how to declare and apply a custom attribute in C#.

Think about how you add extra info to classes or methods.

Describe how to pass parameters to an attribute and why it might be useful.

Consider how you give extra details to the attribute.