Update ValidationContext.MemberName Property to reflect a recent change (dotnet#3470)

* update the doc to reflect a recent change in this property

* Update the doc to reflect on a recent change to MemberName

* Update xml/System.ComponentModel.DataAnnotations/ValidationContext.xml

Co-Authored-By: Maira Wenzel <[email protected]>

* Update xml/System.ComponentModel.DataAnnotations/ValidationContext.xml

Co-Authored-By: Maira Wenzel <[email protected]>

* update - rewordinng for RTM

* Update xml/System.ComponentModel.DataAnnotations/ValidationContext.xml

Co-Authored-By: Maira Wenzel <[email protected]>

* Update xml/System.ComponentModel.DataAnnotations/ValidationContext.xml

Co-Authored-By: Maira Wenzel <[email protected]>

* remove extra space

Author: HongGit

xml/System.ComponentModel.DataAnnotations/ValidationContext.xml

@@ -358,7 +358,7 @@
 
 This property represents an entity member name, not the name of a corresponding data field. Therefore, this name is not localized. It should be set only for property or parameter contexts.
 
-In .NET Framework 4.7.2 and earlier versions, when using a custom <xref:System.ComponentModel.DataAnnotations.ValidationAttribute?displayProperty=nameWithType>, the `MemberName` property returns `null`. Starting with .NET Framework 4.8, the property returns the member name. To restore the previous behavior, you can add the following setting to your app config file:
+In .NET Framework 4.7.2 and earlier versions, when using a custom <xref:System.ComponentModel.DataAnnotations.ValidationAttribute?displayProperty=nameWithType>, the `MemberName` property returns `null`. Starting with [.NET Framework October 2019 Preview of Quality Rollup](https://devblogs.microsoft.com/dotnet/net-framework-october-2019-preview-of-quality-rollup/) for .NET Framework 4.8, the property returns the member name if you add the following setting to your *web.config* file:
 
 ```xml
 <configuration>
@@ -368,6 +368,10 @@ In .NET Framework 4.7.2 and earlier versions, when using a custom <xref:System.C
 </configuration>
 ```
 
+Without this setting, this property returns `null` with .NET Framework October 2019 Preview of Quality Rollup or later versions.
+
+In .NET Framework 4.8 version prior to the October 2019 update, this property returns member name without the configuration setting. If you change your *web.config*  file as shown in the previous example, the property returns `null`.
+
  ]]></format>
         </remarks>
       </Docs>