Update reflection metadata doc

Author: steveharter

xml/System.Reflection.Metadata.Ecma335/MetadataBuilder.xml

@@ -21,7 +21,7 @@
   </Base>
   <Interfaces />
   <Docs>
-    <summary>The MetadataBuilder class reads and writes metadata for an assembly in a highly performant manner. It is designed for use by compilers and other assembly generation tools.</summary>
+    <summary>The MetadataBuilder class writes metadata for an assembly in a highly performant manner. It is designed for use by compilers and other assembly generation tools.</summary>
     <remarks>
       <format type="text/markdown"><![CDATA[  
 

xml/ns-System.Reflection.Metadata.Ecma335.xml

@@ -1,6 +1,17 @@
 <Namespace Name="System.Reflection.Metadata.Ecma335">
   <Docs>
-    <summary>To be added.</summary>
-    <remarks>To be added.</remarks>
-  </Docs>
+    <summary>Provides low-level functionality for writing assembly metadata according to ECMA-335.</summary>
+    <remarks>
+      <format type="text/markdown"><![CDATA[  
+
+## Remarks  
+ This namespace contains the following core classes:  
+  
+-   The <xref:System.Reflection.Metadata.Ecma335.MetadataBuilder> class, which is used to define an assembly.
+
+ ]]></format>
+    </remarks>
+    <altmember cref="N:System.Reflection.Metadata" />    
+    <altmember cref="N:System.Reflection.PortableExecutable" />    
+    </Docs>
 </Namespace>

xml/ns-System.Reflection.Metadata.xml

@@ -1,6 +1,17 @@
 <Namespace Name="System.Reflection.Metadata">
   <Docs>
-    <summary>Contains types that represent metadata information about assemblies, modules, members, parameters, and other entities in managed code.</summary>
-    <remarks></remarks>
-  </Docs>
+    <summary>Provides low-level functionality for reading assembly metadata according to ECMA-335. It is designed for use by compilers and other tools that need to read assembly metadata.</summary>
+    <remarks>
+      <format type="text/markdown"><![CDATA[  
+
+## Remarks  
+ This namespace contains the following core classes:  
+  
+-   The <xref:System.Reflection.Metadata.MetadataReader> class, which is used to read an assembly.
+  
+ ]]></format>
+    </remarks>
+    <altmember cref="N:System.Reflection.Metadata.Ecma335" />    
+    <altmember cref="N:System.Reflection.PortableExecutable" />    
+    </Docs>
 </Namespace>

xml/ns-System.Reflection.PortableExecutable.xml

@@ -1,6 +1,18 @@
 <Namespace Name="System.Reflection.PortableExecutable">
   <Docs>
-    <summary>To be added.</summary>
-    <remarks>To be added.</remarks>
-  </Docs>
+    <summary>Provides classes related to reading or writing Portable Executable (PE) files.</summary>
+    <remarks>
+      <format type="text/markdown"><![CDATA[  
+
+## Remarks  
+ This namespace contains the following core classes:  
+  
+-   The <xref:System.Reflection.PortableExecutable.ManagedPEBuilder> class, which is used to write an assembly as a PE file.
+-   The <xref:System.Reflection.PortableExecutable.PEReader> class, which is used to read a PE file and to obtain a <xref:System.Reflection.Metadata.MetadataReader> to read associated assembly metadata.
+
+ ]]></format>
+    </remarks>
+    <altmember cref="N:System.Reflection.Metadata" />    
+    <altmember cref="N:System.Reflection.Metadata.Ecma335" />    
+    </Docs>
 </Namespace>