Port System.Linq new docs (second pass) (#10216)

Author: carlossanlop

xml/System.Linq/Enumerable.xml

@@ -5674,11 +5674,13 @@ Only unique elements are returned.
         <Parameter Name="source" Type="System.Collections.Generic.IEnumerable&lt;TSource&gt;" RefType="this" Index="0" FrameworkAlternate="net-9.0" />
       </Parameters>
       <Docs>
-        <typeparam name="TSource">To be added.</typeparam>
-        <param name="source">To be added.</param>
-        <summary>To be added.</summary>
+        <typeparam name="TSource">The type of the elements of <paramref name="source" />.</typeparam>
+        <param name="source">The source enumerable providing the elements.</param>
+        <summary>Returns an enumerable that incorporates the element's index into a tuple.</summary>
         <returns>To be added.</returns>
         <remarks>To be added.</remarks>
+        <exception cref="T:System.ArgumentNullException">
+          <paramref name="source" /> is <see langword="null" />.</exception>
       </Docs>
     </Member>
     <MemberGroup MemberName="Intersect&lt;TSource&gt;">

xml/System.Linq/Queryable.xml

@@ -3133,14 +3133,16 @@ The last chunk will contain the remaining elements and may be of a smaller size.
         </Parameter>
       </Parameters>
       <Docs>
-        <typeparam name="TSource">To be added.</typeparam>
-        <typeparam name="TKey">To be added.</typeparam>
-        <param name="source">To be added.</param>
-        <param name="keySelector">To be added.</param>
-        <param name="comparer">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <typeparam name="TSource">The type of the elements of <paramref name="source" />.</typeparam>
+        <typeparam name="TKey">The type of key to distinguish elements by.</typeparam>
+        <param name="source">The sequence to count elements from.</param>
+        <param name="keySelector">A function to extract the key for each element.</param>
+        <param name="comparer">An <see cref="T:System.Collections.Generic.IEqualityComparer`1" /> to compare keys.</param>
+        <summary>Returns the count of each element from a sequence according to a specified key selector function.</summary>
+        <returns>An <see cref="T:System.Linq.IQueryable`1" /> that contains count for each distinct elements from the source sequence as a <see cref="T:System.Collections.Generic.KeyValuePair`2" /> object.</returns>
         <remarks>To be added.</remarks>
+        <exception cref="T:System.ArgumentNullException">
+          <paramref name="source" /> is <see langword="null" />.</exception>
       </Docs>
     </Member>
     <MemberGroup MemberName="DefaultIfEmpty&lt;TSource&gt;">
@@ -5829,11 +5831,13 @@ The last chunk will contain the remaining elements and may be of a smaller size.
         <Parameter Name="source" Type="System.Linq.IQueryable&lt;TSource&gt;" RefType="this" Index="0" FrameworkAlternate="net-9.0" />
       </Parameters>
       <Docs>
-        <typeparam name="TSource">To be added.</typeparam>
-        <param name="source">To be added.</param>
-        <summary>To be added.</summary>
+        <typeparam name="TSource">The type of the elements of <paramref name="source" />.</typeparam>
+        <param name="source">An <see cref="T:System.Linq.IQueryable`1" /> to return an element from.</param>
+        <summary>Return index and the associated item.</summary>
         <returns>To be added.</returns>
         <remarks>To be added.</remarks>
+        <exception cref="T:System.ArgumentNullException">
+          <paramref name="source" /> is <see langword="null" />.</exception>
       </Docs>
     </Member>
     <MemberGroup MemberName="Intersect&lt;TSource&gt;">