Update comment on return value of NetworkStream.Read* variants

Fixes #10925.

Mentions that returns 0 when socket was closed.

Author: rzikm

xml/System.Net.Sockets/NetworkStream.xml

@@ -1107,7 +1107,7 @@ The Close method frees both unmanaged and managed resources associated with the
       <Docs>
         <param name="asyncResult">An <see cref="T:System.IAsyncResult" /> that represents an asynchronous call.</param>
         <summary>Handles the end of an asynchronous read.</summary>
-        <returns>The number of bytes read from the <see cref="T:System.Net.Sockets.NetworkStream" />.</returns>
+        <returns>The number of bytes read from the <see cref="T:System.Net.Sockets.NetworkStream" />, or 0 if the underlying socket was closed.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[
 
@@ -1466,7 +1466,7 @@ The Close method frees both unmanaged and managed resources associated with the
       <Docs>
         <param name="buffer">A region of memory to store data read from the <see cref="T:System.Net.Sockets.NetworkStream" />.</param>
         <summary>Reads data from the <see cref="T:System.Net.Sockets.NetworkStream" /> and stores it to a span of bytes in memory.</summary>
-        <returns>The number of bytes read from the <see cref="T:System.Net.Sockets.NetworkStream" />.</returns>
+        <returns>The number of bytes read from the <see cref="T:System.Net.Sockets.NetworkStream" />, or 0 if the underlying socket was closed.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[
 
@@ -1543,7 +1543,7 @@ There is a failure reading from the network.</exception>
         <param name="size">The number of bytes to read from the <see cref="T:System.Net.Sockets.NetworkStream" />.</param>
         <param name="count">The number of bytes to read from the <see cref="T:System.Net.Sockets.NetworkStream" />.</param>
         <summary>Reads data from the <see cref="T:System.Net.Sockets.NetworkStream" /> and stores it to a byte array.</summary>
-        <returns>The number of bytes read from the <see cref="T:System.Net.Sockets.NetworkStream" />.</returns>
+        <returns>The number of bytes read from the <see cref="T:System.Net.Sockets.NetworkStream" />, or 0 if the underlying socket was closed.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[
 
@@ -1695,7 +1695,7 @@ There is a failure reading from the network.</exception>
         <param name="buffer">The buffer to write the data to.</param>
         <param name="cancellationToken">The token to monitor for cancellation requests.</param>
         <summary>Reads data from the <see cref="T:System.Net.Sockets.NetworkStream" /> and stores it in a byte memory range as an asynchronous operation.</summary>
-        <returns>A <see cref="T:System.Threading.Tasks.ValueTask`1" /> that represents the asynchronous read operation. The value of its <see cref="P:System.Threading.Tasks.ValueTask`1.Result" /> property contains the total number of bytes read into <paramref name="buffer" />.</returns>
+        <returns>A <see cref="T:System.Threading.Tasks.ValueTask`1" /> that represents the asynchronous read operation. The value of its <see cref="P:System.Threading.Tasks.ValueTask`1.Result" /> property contains the total number of bytes read into <paramref name="buffer" />, or 0 if the underlying socket was closed.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[
 
@@ -1766,7 +1766,7 @@ There is a failure reading from the network.</exception>
         <param name="count">The number of bytes to read from the <see cref="T:System.Net.Sockets.NetworkStream" />.</param>
         <param name="cancellationToken">The token to monitor for cancellation requests.</param>
         <summary>Reads data from the <see cref="T:System.Net.Sockets.NetworkStream" /> and stores it to a specified range of a byte array as an asynchronous operation.</summary>
-        <returns>A task that represents the asynchronous read operation. The value of its <see cref="P:System.Threading.Tasks.Task`1.Result" /> property contains the total number of bytes read into <paramref name="buffer" />.</returns>
+        <returns>A task that represents the asynchronous read operation. The value of its <see cref="P:System.Threading.Tasks.Task`1.Result" /> property contains the total number of bytes read into <paramref name="buffer" />, or 0 if the underlying socket was closed.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[