Documentation for expression-bodied members in C# 7 by rpetrusha · Pull Request #2101 · dotnet/docs

rpetrusha · 2017-05-05T23:57:01Z

Documentation for expression-bodied members in C# 7

Summary

Documents expression body definitions, and also mentions expression body definitions in each supported member topic that did not mention it.

Also revised the top-level constructor topic somewhat.

Fixes #1789

Suggested Reviewers

@BillWagner

mairaw

Since the builds are failing, did just a quick review

mairaw · 2017-05-10T05:48:22Z

docs/csharp/programming-guide/statements-expressions-operators/expressions.md

 In the following code example, the call to `DoWork` is an invocation expression.  

-```  
+```cs


the label supported by OPS is csharp

mairaw · 2017-05-10T05:50:50Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+
+The following example defines a `Person` class that overrides the <xref:System.Object.ToString</xref> method with an expression body definition. It also defines a `Show` method that displays a name to the console. Note that the `return` keyword is not used in the `ToString` expression body definition.
+
+[!code-cs[expression-bodied-methods](../../../../samples/snippets/csharp/programming-guide/classes-and-structs/expr-bodied-methods.cs#1)]  


build is complaining about this line. the snippet code doesn't have any tags.

mairaw · 2017-05-10T05:51:18Z

docs/csharp/programming-guide/classes-and-structs/constructors.md

- If you do not provide a constructor for your object, C# will create one by default that instantiates the object and sets member variables to the default values as listed in [Default Values Table](../../../csharp/language-reference/keywords/default-values-table.md). For more information and examples, see [Instance Constructors](../../../csharp/programming-guide/classes-and-structs/instance-constructors.md).  
-
- Static classes and structs can also have constructors. For more information and examples, see [Static Constructors](../../../csharp/programming-guide/classes-and-structs/static-constructors.md).  
+If you do not provide a constructor for your class, C# creates one by default that instantiates the object and sets member variables to the default values as listed in the [Default Values Table](../../../csharp/language-reference/keywords/default-values-table.md). If you do not provide a constructor for your struct, C# replies on an *implicit default constructor* to automatically initialize each field of a value type to its default value as listed in the [Default Values Table](../../../csharp/language-reference/keywords/default-values-table.md). For more information and examples, see [Instance Constructors](../../../csharp/programming-guide/classes-and-structs/instance-constructors.md).  


nit: do not -> don't

mairaw · 2017-05-10T05:54:24Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+  - "C# language, expresion-bodied members"
+author: "rpetrusha"
+ms.author: "ronpet"
+translation.priority.ht: 


I don't think we need this in new articles

mairaw · 2017-05-10T05:55:23Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+
+where *expression* is any valid expression. 
+
+Support for expression body definitions was introduced for methods and property get accessors in C# 6 and was expanded in C# 7. Expression body definitions can be used with the type members listed in the following table. 


nit: end with colon

mairaw · 2017-05-10T05:55:41Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+
+## Methods
+
+An expression-bodied method consists of a single expression that returns a value whose type matches the method's return type, or, for methods that return `void`, that performs some operation. For example, types that override the <xref:System.Object.ToString</xref> method typically include a single expression that returns the string representation of the current object. 


this xref link will probably fail

mairaw · 2017-05-10T05:56:33Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+
+## Property get statements
+
+If you choose to implement a property get accessor yourself, you can use an expression body definition for single-line statements that simply return the the proeprty value. Note that the `return` statement is not used.


the the proeprty -> the property

should get be inline code here?

is not -> isn't

mairaw · 2017-05-10T05:57:59Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+
+An expression-bodied method consists of a single expression that returns a value whose type matches the method's return type, or, for methods that return `void`, that performs some operation. For example, types that override the <xref:System.Object.ToString</xref> method typically include a single expression that returns the string representation of the current object. 
+
+The following example defines a `Person` class that overrides the <xref:System.Object.ToString</xref> method with an expression body definition. It also defines a `Show` method that displays a name to the console. Note that the `return` keyword is not used in the `ToString` expression body definition.


same here for this xref link

rpetrusha · 2017-05-10T19:39:20Z

Thanks, @mairaw. I've incorporated your corrections.

BillWagner

Overall, this looks great. I left a few comments. One is a recent language spec change that has C# standardizing on "finalizer" over "destructor".

The background is that "destructor" sounded too much like "deconstruction" which was added with tuples. And, both terms were used interchangeably, so picking one made sense.

BillWagner · 2017-05-10T21:13:01Z

docs/csharp/programming-guide/classes-and-structs/destructors.md


 [!code-cs[csProgGuideObjects#86](../../../csharp/programming-guide/classes-and-structs/codesnippet/CSharp/destructors_1.cs)]  
+
+A destructor can also be implemented as an expression body definition, as the following example shows.


The official language spec is going to standardize on 'finalizer' over 'destructor'. (Both had been used previously.

We should match that.

BillWagner · 2017-05-10T21:13:20Z

docs/csharp/programming-guide/classes-and-structs/destructors.md

+[!code-cs[expression-bodied-destructor](../../../../samples/snippets/csharp/programming-guide/classes-and-structs/expr-bodied-destructor.cs#1)]  

- The destructor implicitly calls <xref:System.Object.Finalize%2A> on the base class of the object. Therefore, the previous destructor code is implicitly translated to the following code:  
+ The destructor implicitly calls <xref:System.Object.Finalize%2A> on the base class of the object. Therefore, a call to a destructor is implicitly translated to the following code:  


destructor => finalizer.

BillWagner · 2017-05-10T21:14:44Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+member => expression;
+```
+
+where *expression* is any valid expression. 


I'd say 'a valid expression' instead of 'any valid expression'. I can't think of any disallowed off the top of my head, but I bet if I thought hard enough I could find one.

BillWagner · 2017-05-10T21:15:53Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+
+## Constructors
+
+An expression body definition for a constructor typically consists of a single assignment statement or a method call that handles the constructor's arguments or initializes instance state. 


nit: 'assignment statement' should be 'assignment expression'

BillWagner · 2017-05-10T21:16:10Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+
+## Destructors
+
+An expression body definition for a destructor typically contains cleanup statements, such as statements that release unmanaged resources.


BillWagner · 2017-05-10T21:16:16Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+
+For more information, see [Constructors (C# Programming Guide)](../classes-and-structs/constructors.md).
+
+## Destructors


Finalizers.

BillWagner · 2017-05-10T21:16:38Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+
+An expression body definition for a destructor typically contains cleanup statements, such as statements that release unmanaged resources.
+
+The following example defines a destructor that uses an expression body definition to indicate that the destructor has been called.


finalizer (twice)

BillWagner · 2017-05-10T21:17:16Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+
+[!code-cs[expression-bodied-destructor](../../../../samples/snippets/csharp/programming-guide/classes-and-structs/expr-bodied-destructor.cs#1)]  
+
+For more information, see [Destructors (C# Programming Guide)](../classes-and-structs/destructors.md).


I know we haven't updated the programming guide, but what do you think of the link text as "Finalizers" instead of "Destructors"?

BillWagner · 2017-05-10T21:18:33Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+
+## Property get statements
+
+If you choose to implement a property get accessor yourself, you can use an expression body definition for single-line statements that simply return the property value. Note that the `return` statement isn't used.


I'd say "single expression" instead of "single-line statement".

For example, a LINQ query is a single expression, but might span multiple lines.

rpetrusha · 2017-05-10T23:16:12Z

@BillWagner, I've addressed your comments and also changed destructor -> finalizer throughout the doc set.

BillWagner · 2017-05-11T00:45:54Z

Wow. Thanks for checking everywhere for the destructor -> finalizer change @rpetrusha

mairaw

LGTM. There are still some snippets using the cs indentifier instead of csharp though.

mairaw · 2017-05-15T18:24:38Z

docs/csharp/programming-guide/statements-expressions-operators/expression-bodied-members.md

+
+Read-only properties that use an expression body definition can be implemented without an explicit `set` statement. The syntax is:
+
+```cs


i only commented once, but all places need to switch from ```cs to ```csharp

mairaw · 2017-05-15T18:27:57Z

docs/csharp/programming-guide/classes-and-structs/constructors.md

- If you do not provide a constructor for your object, C# will create one by default that instantiates the object and sets member variables to the default values as listed in [Default Values Table](../../../csharp/language-reference/keywords/default-values-table.md). For more information and examples, see [Instance Constructors](../../../csharp/programming-guide/classes-and-structs/instance-constructors.md).  
-
- Static classes and structs can also have constructors. For more information and examples, see [Static Constructors](../../../csharp/programming-guide/classes-and-structs/static-constructors.md).  
+If you don't provide a constructor for your class, C# creates one by default that instantiates the object and sets member variables to the default values as listed in the [Default Values Table](../../../csharp/language-reference/keywords/default-values-table.md). If you do not provide a constructor for your struct, C# replies on an *implicit default constructor* to automatically initialize each field of a value type to its default value as listed in the [Default Values Table](../../../csharp/language-reference/keywords/default-values-table.md). For more information and examples, see [Instance Constructors](../../../csharp/programming-guide/classes-and-structs/instance-constructors.md).  


nit: there a few more contractions to be made: do not -> don't

rpetrusha · 2017-05-15T19:48:52Z

Thanks, @mairaw. I've changed "cs" to "csharp" and replaced "do not" with "don't". I'll merge when this publishes.

Ron Petrusha added 2 commits May 5, 2017 13:24

Expression-bodied members topic

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Remaining expression-bodied member changes

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mairaw requested changes May 10, 2017

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Addressed review comments

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BillWagner requested changes May 10, 2017

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Addressed review comments, changed 'destructor' to 'finalizer'

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BillWagner approved these changes May 11, 2017

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mairaw approved these changes May 15, 2017

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Addressed remaining review comments

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rpetrusha merged commit a5ed524 into dotnet:master May 15, 2017

rpetrusha deleted the exp-bodied branch May 15, 2017 21:06


		The following example defines a `Person` class that overrides the <xref:System.Object.ToString</xref> method with an expression body definition. It also defines a `Show` method that displays a name to the console. Note that the `return` keyword is not used in the `ToString` expression body definition.

		[!code-cs[expression-bodied-methods](../../../../samples/snippets/csharp/programming-guide/classes-and-structs/expr-bodied-methods.cs#1)]


		where expression is any valid expression.

		Support for expression body definitions was introduced for methods and property get accessors in C# 6 and was expanded in C# 7. Expression body definitions can be used with the type members listed in the following table.


		## Methods

		An expression-bodied method consists of a single expression that returns a value whose type matches the method's return type, or, for methods that return `void`, that performs some operation. For example, types that override the <xref:System.Object.ToString</xref> method typically include a single expression that returns the string representation of the current object.


		## Property get statements

		If you choose to implement a property get accessor yourself, you can use an expression body definition for single-line statements that simply return the the proeprty value. Note that the `return` statement is not used.


		[!code-cs[csProgGuideObjects#86](../../../csharp/programming-guide/classes-and-structs/codesnippet/CSharp/destructors_1.cs)]

		A destructor can also be implemented as an expression body definition, as the following example shows.


		## Constructors

		An expression body definition for a constructor typically consists of a single assignment statement or a method call that handles the constructor's arguments or initializes instance state.


		## Destructors

		An expression body definition for a destructor typically contains cleanup statements, such as statements that release unmanaged resources.


		For more information, see [Constructors (C# Programming Guide)](../classes-and-structs/constructors.md).

		## Destructors


		An expression body definition for a destructor typically contains cleanup statements, such as statements that release unmanaged resources.

		The following example defines a destructor that uses an expression body definition to indicate that the destructor has been called.


		[!code-cs[expression-bodied-destructor](../../../../samples/snippets/csharp/programming-guide/classes-and-structs/expr-bodied-destructor.cs#1)]

		For more information, see [Destructors (C# Programming Guide)](../classes-and-structs/destructors.md).


		Read-only properties that use an expression body definition can be implemented without an explicit `set` statement. The syntax is:

		```cs

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rpetrusha commented May 5, 2017

Documentation for expression-bodied members in C# 7

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rpetrusha commented May 10, 2017

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rpetrusha commented May 10, 2017

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rpetrusha commented May 15, 2017

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