Add remarks about EventSource.GetGuid (dotnet#5209)

* Add remarks about EventSource.GetGuid returning different value from EventSource.Guid property

* fix build warnings'

* PR feedback

* fix incorrect xref

* apply PR feedback

* Apply suggestions from code review

Co-authored-by: Genevieve Warren <[email protected]>

* Update xml/System.Diagnostics.Tracing/EventSource.xml

Co-authored-by: Genevieve Warren <[email protected]>

* more code review feedback

Co-authored-by: Genevieve Warren <[email protected]>

Author: sywhang

xml/System.Diagnostics.Tracing/EventSource.xml

@@ -241,7 +241,15 @@
       <Docs>
         <param name="eventSourceName">The name to apply to the event source. Must not be <see langword="null" />.</param>
         <summary>Creates a new instance of the <see cref="T:System.Diagnostics.Tracing.EventSource" /> class with the specified name.</summary>
-        <remarks>To be added.</remarks>
+        <remarks>
+          <format type="text/markdown"><![CDATA[
+  ## Remarks
+
+  When using this constructor, ensure that the `eventSourceName` argument matches the ETW name defined by the <xref:System.Diagnostics.Tracing.EventSourceAttribute> attribute on that type. Otherwise, the GUIDs returned by the <xref:System.Diagnostics.Tracing.EventSource.Guid> property and the <xref:System.Diagnostics.Tracing.EventSource.GetGuid(System.Type)> method will be different. If the event source names differ, the <xref:System.Diagnostics.Tracing.EventSource.Guid> property returns the GUID used to register this EventSource with ETW.
+
+
+          ]]></format>
+        </remarks>
         <exception cref="T:System.ArgumentNullException">
           <paramref name="eventSourceName" /> is <see langword="null" />.</exception>
       </Docs>
@@ -295,8 +303,8 @@
 ## Remarks  
  Traits provide additional information for an event and are interpreted by an event listener. Traits are specified as key-value pairs and if not specified in pairs, an exception will occur. You can retrieve a trait by passing the key to the <xref:System.Diagnostics.Tracing.EventSource.GetTrait%2A>, method.  
   
- Specifying `settings` when the <xref:System.Diagnostics.Tracing.EventSource> is constructed enables you to  specify whether the event is written in a manifest-based or a self-describing format. In addition, you can specify that an exception should be raised when an error occurs during the event-writing process.  
-  
+ Specifying `settings` when the <xref:System.Diagnostics.Tracing.EventSource> is constructed enables you to specify whether the event is written in a manifest-based or a self-describing format. In addition, you can specify that an exception should be raised when an error occurs during the event-writing process.
+
  ]]></format>
         </remarks>
         <exception cref="T:System.ArgumentException">
@@ -343,8 +351,12 @@
           <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- Specifying `settings` when the <xref:System.Diagnostics.Tracing.EventSource> is constructed enables you to  specify whether the event is written in a manifest-based or a self-describing format. In addition, you can specify that an exception should be raised when an error occurs during the event-writing process.  
-  
+ Specifying `settings` when the <xref:System.Diagnostics.Tracing.EventSource> is constructed enables you to specify whether the event is written in a manifest-based or a self-describing format. In addition, you can specify that an exception should be raised when an error occurs during the event-writing process.
+
+ When using this constructor, ensure that the `eventSourceName` argument matches the ETW name defined by the <xref:System.Diagnostics.Tracing.EventSourceAttribute> attribute on that type. Otherwise, the GUIDs returned by the <xref:System.Diagnostics.Tracing.EventSource.Guid> property and the <xref:System.Diagnostics.Tracing.EventSource.GetGuid(System.Type)> method will be different.
+
+ In such cases, the <xref:System.Diagnostics.Tracing.EventSource.Guid> property returns the GUID used to register this EventSource with ETW.
+
  ]]></format>
         </remarks>
         <exception cref="T:System.ArgumentNullException">
@@ -402,8 +414,11 @@
 ## Remarks  
  Traits provide additional information for an event and are interpreted by an event listener. Traits are specified as key-value pairs and if not specified in pairs, an exception will occur. You can retrieve a trait by passing the key to the <xref:System.Diagnostics.Tracing.EventSource.GetTrait%2A>, method.  
   
- Specifying `config` when the <xref:System.Diagnostics.Tracing.EventSource> is constructed enables you to  specify whether the event is written in a manifest-based or a self-describing format. In addition, you can specify that an exception should be raised when an error occurs during the event-writing process.  
-  
+ Specifying `config` when the <xref:System.Diagnostics.Tracing.EventSource> is constructed enables you to specify whether the event is written in a manifest-based or a self-describing format. In addition, you can specify that an exception should be raised when an error occurs during the event-writing process.
+ 
+ When using this constructor, ensure that the `eventSourceName` argument matches the ETW name defined by the <xref:System.Diagnostics.Tracing.EventSourceAttribute> attribute on that type. Otherwise, the GUIDs returned by the <xref:System.Diagnostics.Tracing.EventSource.Guid> property and the <xref:System.Diagnostics.Tracing.EventSource.GetGuid(System.Type)> method will be different.
+
+ In such cases, the GUID used to register this EventSource with ETW is the one returned by <xref:System.Diagnostics.Tracing.EventSource.Guid>.
  ]]></format>
         </remarks>
         <exception cref="T:System.ArgumentNullException">
@@ -863,7 +878,14 @@
         <param name="eventSourceType">The type of the event source.</param>
         <summary>Gets the unique identifier for this implementation of the event source.</summary>
         <returns>A unique identifier for this event source type.</returns>
-        <remarks>To be added.</remarks>
+        <remarks>
+          <format type="text/markdown"><![CDATA[
+## Remarks
+If the name of the <xref:System.Diagnostics.Tracing.EventSource> that was passed to the constructor isn't specified as an <xref:System.Diagnostics.Tracing.EventSourceAttribute>, this method can return a different GUID to the one returned by the <xref:System.Diagnostics.Tracing.EventSource.Guid> property.
+
+In such cases, the GUID that is used to register the <xref:System.Diagnostics.Tracing.EventSource> is the one returned by <xref:System.Diagnostics.Tracing.EventSource.Guid> property.
+  ]]>]</format>
+        </remarks>
       </Docs>
     </Member>
     <Member MemberName="GetName">