Define group value order (#3429)

Documents that the grouping is stable.

Author: breyed

xml/System.Linq/Enumerable.xml

@@ -11803,7 +11803,7 @@ If `count` is not a positive number, this method returns an empty enumerable col
         <param name="source">An <see cref="T:System.Collections.Generic.IEnumerable`1" /> to create a <see cref="T:System.Collections.Generic.Dictionary`2" /> from.</param>
         <param name="keySelector">A function to extract a key from each element.</param>
         <summary>Creates a <see cref="T:System.Collections.Generic.Dictionary`2" /> from an <see cref="T:System.Collections.Generic.IEnumerable`1" /> according to a specified key selector function.</summary>
-        <returns>A <see cref="T:System.Collections.Generic.Dictionary`2" /> that contains keys and values.</returns>
+        <returns>A <see cref="T:System.Collections.Generic.Dictionary`2" /> that contains keys and values. The values within each group are in the same order as in <paramref name="source" />.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[  
 
@@ -11876,7 +11876,7 @@ If `count` is not a positive number, this method returns an empty enumerable col
         <param name="keySelector">A function to extract a key from each element.</param>
         <param name="comparer">An <see cref="T:System.Collections.Generic.IEqualityComparer`1" /> to compare keys.</param>
         <summary>Creates a <see cref="T:System.Collections.Generic.Dictionary`2" /> from an <see cref="T:System.Collections.Generic.IEnumerable`1" /> according to a specified key selector function and key comparer.</summary>
-        <returns>A <see cref="T:System.Collections.Generic.Dictionary`2" /> that contains keys and values.</returns>
+        <returns>A <see cref="T:System.Collections.Generic.Dictionary`2" /> that contains keys and values. The values within each group are in the same order as in <paramref name="source" />.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[  
 
@@ -12234,7 +12234,7 @@ If `count` is not a positive number, this method returns an empty enumerable col
         <param name="source">The <see cref="T:System.Collections.Generic.IEnumerable`1" /> to create a <see cref="T:System.Linq.Lookup`2" /> from.</param>
         <param name="keySelector">A function to extract a key from each element.</param>
         <summary>Creates a <see cref="T:System.Linq.Lookup`2" /> from an <see cref="T:System.Collections.Generic.IEnumerable`1" /> according to a specified key selector function.</summary>
-        <returns>A <see cref="T:System.Linq.Lookup`2" /> that contains keys and values.</returns>
+        <returns>A <see cref="T:System.Linq.Lookup`2" /> that contains keys and values. The values within each group are in the same order as in <paramref name="source" />.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[  
 
@@ -12295,7 +12295,7 @@ If `count` is not a positive number, this method returns an empty enumerable col
         <param name="keySelector">A function to extract a key from each element.</param>
         <param name="comparer">An <see cref="T:System.Collections.Generic.IEqualityComparer`1" /> to compare keys.</param>
         <summary>Creates a <see cref="T:System.Linq.Lookup`2" /> from an <see cref="T:System.Collections.Generic.IEnumerable`1" /> according to a specified key selector function and key comparer.</summary>
-        <returns>A <see cref="T:System.Linq.Lookup`2" /> that contains keys and values.</returns>
+        <returns>A <see cref="T:System.Linq.Lookup`2" /> that contains keys and values. The values within each group are in the same order as in <paramref name="source" />.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[