Added overview of C# member access operators (#12240)

* Added overview of C# member access operators

* Updated TOC

* Use indexer operator

* Minor edits

* Setup redirection

* Minor edits

* Addressed feedback

Author: pkulikov

.openpublishing.redirection.json

@@ -482,6 +482,10 @@
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             "redirect_url":"/dotnet/csharp/language-reference/operators/arithmetic-operators#increment-operator-"
         },
+        {
+            "source_path": "docs/csharp/language-reference/operators/index-operator.md",
+            "redirect_url": "/dotnet/csharp/language-reference/operators/member-access-operators#indexer-operator-"
+        },
         {
             "source_path":"docs/csharp/language-reference/operators/left-shift-assignment-operator.md",
             "redirect_url":"/dotnet/csharp/language-reference/operators/bitwise-and-shift-operators#compound-assignment"
@@ -502,6 +506,10 @@
             "source_path":"docs/csharp/language-reference/operators/logical-negation-operator.md",
             "redirect_url":"/dotnet/csharp/language-reference/operators/boolean-logical-operators#logical-negation-operator-"
         },
+        {
+            "source_path": "docs/csharp/language-reference/operators/member-access-operator.md",
+            "redirect_url": "/dotnet/csharp/language-reference/operators/member-access-operators#member-access-operator-"
+        },
         {
             "source_path": "docs/csharp/language-reference/operators/modulus-assignment-operator.md",
             "redirect_url": "/dotnet/csharp/language-reference/operators/arithmetic-operators#compound-assignment"
@@ -518,6 +526,10 @@
             "source_path": "docs/csharp/language-reference/operators/null-conditional-operator.md",
             "redirect_url": "/dotnet/csharp/language-reference/operators/null-coalescing-operator"
         },
+        {
+            "source_path": "docs/csharp/language-reference/operators/null-conditional-operators.md",
+            "redirect_url": "/dotnet/csharp/language-reference/operators/member-access-operators#null-conditional-operators--and-"
+        },
         {
             "source_path":"docs/csharp/language-reference/operators/or-assignment-operator.md",
             "redirect_url":"/dotnet/csharp/language-reference/operators/boolean-logical-operators#compound-assignment"

docs/csharp/language-reference/compiler-messages/cs0201.md

@@ -11,11 +11,11 @@ ms.assetid: cf5d6701-50cc-4e4f-878b-e1a4ad8a2061
 
 Only assignment, call, increment, decrement, and new object expressions can be used as a statement  
 
- The compiler generates an error when it encounters an invalid statement. An invalid statement is any line or series of lines ending in a semicolon that does not represent an assignment ([=](../operators/assignment-operator.md)), method call [()](../operators/invocation-operator.md), [new](../keywords/new.md), [--](../operators/arithmetic-operators.md#decrement-operator---) or [++](../operators/arithmetic-operators.md#increment-operator-) operation. For more information, see [Statements, Expressions, and Operators](../../programming-guide/statements-expressions-operators/index.md).  
+ The compiler generates an error when it encounters an invalid statement. An invalid statement is any line or series of lines ending in a semicolon that does not represent an assignment ([=](../operators/assignment-operator.md)), method call [()](../operators/member-access-operators.md#invocation-operator-), [new](../keywords/new.md), [--](../operators/arithmetic-operators.md#decrement-operator---) or [++](../operators/arithmetic-operators.md#increment-operator-) operation. For more information, see [Statements, Expressions, and Operators](../../programming-guide/statements-expressions-operators/index.md).  
 
 ## Example
 
- The following sample generates CS0201 because 2 * 3 is an expression, not a statement. To make the code compile, try assigning the value of the expression to a  variable.  
+ The following sample generates CS0201 because 2 * 3 is an expression, not a statement. To make the code compile, try assigning the value of the expression to a variable.  
 
 ```csharp
 // CS0201.cs  

docs/csharp/language-reference/keywords/extern-alias.md

@@ -1,7 +1,6 @@
 ---
 title: "extern alias - C# Reference"
 ms.custom: seodec18
-
 ms.date: 07/20/2015
 f1_keywords: 
   - "alias_CSharpKeyword"

docs/csharp/language-reference/keywords/namespace-keywords.md

@@ -1,25 +1,25 @@
 ---
 title: "Namespace Keywords - C# Reference"
 ms.custom: seodec18
-
 ms.date: 07/20/2015
 helpviewer_keywords: 
   - "namespaces [C#], keywords"
 ms.assetid: 091a66eb-b10d-4f54-9102-5ac0d4bdb84b
 ---
 # Namespace Keywords (C# Reference)
+
 This section describes the keywords and operators that are associated with using namespaces:  
 
-- [namespace](../../../csharp/language-reference/keywords/namespace.md)  
-- [using](../../../csharp/language-reference/keywords/using.md)  
+- [namespace](namespace.md)  
+- [using](using-directive.md)  
 - [using static](using-static.md)
-- [. Operator](../../../csharp/language-reference/operators/member-access-operator.md)  
-- [:: Operator](../../../csharp/language-reference/operators/namespace-alias-qualifer.md)  
-- [extern alias](../../../csharp/language-reference/keywords/extern-alias.md)  
+- [. Operator](../operators/member-access-operators.md#member-access-operator-)  
+- [:: Operator](../operators/namespace-alias-qualifer.md)  
+- [extern alias](extern-alias.md)  
 
 ## See also
 
-- [C# Reference](../../../csharp/language-reference/index.md)
-- [C# Programming Guide](../../../csharp/programming-guide/index.md)
-- [C# Keywords](../../../csharp/language-reference/keywords/index.md)
-- [Namespaces](../../../csharp/programming-guide/namespaces/index.md)
+- [C# Reference](../index.md)
+- [C# Programming Guide](../../programming-guide/index.md)
+- [C# Keywords](index.md)
+- [Namespaces](../../programming-guide/namespaces/index.md)

docs/csharp/language-reference/keywords/using.md

@@ -12,8 +12,9 @@ ms.assetid: 124e1a63-2a4b-4132-b269-3b6d8d3ef72d
 # using (C# Reference)
 
 The `using` keyword has three major uses:
-- The [using statement](using-statement.md) defines a scope at the end of which an object will be disposed. 
-- The using [directive](using-directive.md) creates an alias for a namespace or imports types defined in other namespaces. 
+
+- The [using statement](using-statement.md) defines a scope at the end of which an object will be disposed.
+- The [using directive](using-directive.md) creates an alias for a namespace or imports types defined in other namespaces.
 - The [using static directive](using-static.md) imports the members of a single class.
 
 ## See also

docs/csharp/language-reference/operators/conditional-operator.md

@@ -1,7 +1,6 @@
 ---
 title: "?: Operator - C# Reference"
 ms.custom: seodec18
-
 ms.date: "11/20/2018"
 f1_keywords:
   - "?:_CSharpKeyword"
@@ -38,9 +37,9 @@ is evaluated as
 a ? b : (c ? d : e)
 ```
 
-A handy mnemonic device you can use to remember how this operator evaluates is by asking:
+A mnemonic device you can use to remember how this operator evaluates is to ask:
 
-```
+```text
 is this condition true ? yes : no
 ```
 
@@ -90,6 +89,6 @@ For more information, see the [Conditional operator](~/_csharplang/spec/expressi
 - [C# Programming Guide](../../programming-guide/index.md)
 - [C# Operators](index.md)
 - [if-else statement](../keywords/if-else.md)
-- [?. and ?[] Operators](null-conditional-operators.md)
+- [?. and ?[] Operators](member-access-operators.md#null-conditional-operators--and-)
 - [?? Operator](null-coalescing-operator.md)
 - [ref keyword](../keywords/ref.md)

docs/csharp/language-reference/operators/index-operator.md

@@ -31,15 +31,15 @@ The following sections list the C# operators starting with the highest precedenc
 
 These are the highest precedence operators.
 
-[x.y](member-access-operator.md) – member access.
+[x.y](member-access-operators.md#member-access-operator-) – member access.
 
-[x?.y](null-conditional-operators.md) – null conditional member access. Returns `null` if the left-hand operand evaluates to `null`.
+[x?.y](member-access-operators.md#null-conditional-operators--and-) – null conditional member access. Returns `null` if the left-hand operand evaluates to `null`.
 
-[x?[y]](null-conditional-operators.md) - null conditional index access. Returns `null` if the left-hand operand evaluates to `null`.
+[x?[y]](member-access-operators.md#null-conditional-operators--and-) - null conditional array element or type indexer access. Returns `null` if the left-hand operand evaluates to `null`.
 
-[f(x)](invocation-operator.md) – function invocation.
+[f(x)](member-access-operators.md#invocation-operator-) – method call or delegate invocation.
 
-[a[x]](index-operator.md) – aggregate object indexing.
+[a[x]](member-access-operators.md#indexer-operator-) – array element or type indexer access.
 
 [x++](arithmetic-operators.md#increment-operator-) – postfix increment. Returns the value of x and then updates the storage location with the value of x that is one greater (typically adds the integer 1).