Update remarks and exceptions for MaxBy/MinBy (#9321)

Author: gewarren

xml/System.Linq/Enumerable.xml

@@ -8257,18 +8257,13 @@ In Visual Basic query expression syntax, an `Aggregate Into Max()` clause transl
         <param name="keySelector">A function to extract the key for each element.</param>
         <summary>Returns the maximum value in a generic sequence according to a specified key selector function.</summary>
         <returns>The value with the maximum key in the sequence.</returns>
-        <remarks>
-          <format type="text/markdown"><![CDATA[
-
-## Remarks
-
-If `TKey` is a reference type and the source sequence is empty or contains only values that are `null`, this method returns `null`.
-
-          ]]></format>
-        </remarks>
+        <remarks><para>If the source sequence is empty and <typeparamref name="TSource" /> is a nullable type, this method returns <see langword="null" />. If the source sequence is empty and <typeparamref name="TSource" /> is a non-nullable struct, such as a primitive type, an <see cref="T:System.InvalidOperationException" /> is thrown.</para>
+        <para>If the source sequence contains only values that are <see langword="null" />.</para></remarks>
         <exception cref="T:System.ArgumentNullException">
           <paramref name="source" /> is <see langword="null" />.</exception>
         <exception cref="T:System.ArgumentException">No key extracted from <paramref name="source" /> implements the <see cref="T:System.IComparable" /> or <see cref="T:System.IComparable`1" /> interface.</exception>
+        <exception cref="T:System.InvalidOperationException">
+          <typeparamref name="TSource" /> is a primitive type and the source sequence is empty.</exception>
       </Docs>
     </Member>
     <Member MemberName="MaxBy&lt;TSource,TKey&gt;">
@@ -8338,18 +8333,13 @@ If `TKey` is a reference type and the source sequence is empty or contains only
         <param name="comparer">The <see cref="T:System.Collections.Generic.IComparer`1" /> to compare keys.</param>
         <summary>Returns the maximum value in a generic sequence according to a specified key selector function and key comparer.</summary>
         <returns>The value with the maximum key in the sequence.</returns>
-        <remarks>
-          <format type="text/markdown"><![CDATA[
-
-## Remarks
-
-If `TKey` is a reference type and the source sequence is empty or contains only values that are `null`, this method returns `null`.
-
-          ]]></format>
-        </remarks>
+        <remarks><para>If the source sequence is empty and <typeparamref name="TSource" /> is a nullable type, this method returns <see langword="null" />. If the source sequence is empty and <typeparamref name="TSource" /> is a non-nullable struct, such as a primitive type, an <see cref="T:System.InvalidOperationException" /> is thrown.</para>
+        <para>If the source sequence contains only values that are <see langword="null" />.</para></remarks>
         <exception cref="T:System.ArgumentNullException">
           <paramref name="source" /> is <see langword="null" />.</exception>
         <exception cref="T:System.ArgumentException">No key extracted from <paramref name="source" /> implements the <see cref="T:System.IComparable" /> or <see cref="T:System.IComparable`1" /> interface.</exception>
+        <exception cref="T:System.InvalidOperationException">
+          <typeparamref name="TSource" /> is a primitive type and the source sequence is empty.</exception>
       </Docs>
     </Member>
     <MemberGroup MemberName="Min">
@@ -10061,18 +10051,13 @@ In Visual Basic query expression syntax, an `Aggregate Into Min()` clause transl
         <param name="keySelector">A function to extract the key for each element.</param>
         <summary>Returns the minimum value in a generic sequence according to a specified key selector function.</summary>
         <returns>The value with the minimum key in the sequence.</returns>
-        <remarks>
-          <format type="text/markdown"><![CDATA[
-
-## Remarks
-
-If `TKey` is a reference type and the source sequence is empty or contains only values that are `null`, this method returns `null`.
-
-          ]]></format>
-        </remarks>
+        <remarks><para>If the source sequence is empty and <typeparamref name="TSource" /> is a nullable type, this method returns <see langword="null" />. If the source sequence is empty and <typeparamref name="TSource" /> is a non-nullable struct, such as a primitive type, an <see cref="T:System.InvalidOperationException" /> is thrown.</para>
+        <para>If the source sequence contains only values that are <see langword="null" />.</para></remarks>
         <exception cref="T:System.ArgumentNullException">
           <paramref name="source" /> is <see langword="null" />.</exception>
         <exception cref="T:System.ArgumentException">No key extracted from <paramref name="source" /> implements the <see cref="T:System.IComparable" /> or <see cref="T:System.IComparable`1" /> interface.</exception>
+        <exception cref="T:System.InvalidOperationException">
+          <typeparamref name="TSource" /> is a primitive type and the source sequence is empty.</exception>
       </Docs>
     </Member>
     <Member MemberName="MinBy&lt;TSource,TKey&gt;">
@@ -10142,18 +10127,13 @@ If `TKey` is a reference type and the source sequence is empty or contains only
         <param name="comparer">The <see cref="T:System.Collections.Generic.IComparer`1" /> to compare keys.</param>
         <summary>Returns the minimum value in a generic sequence according to a specified key selector function and key comparer.</summary>
         <returns>The value with the minimum key in the sequence.</returns>
-        <remarks>
-          <format type="text/markdown"><![CDATA[
-
-## Remarks
-
-If `TKey` is a reference type and the source sequence is empty or contains only values that are `null`, this method returns `null`.
-
-          ]]></format>
-        </remarks>
+        <remarks><para>If the source sequence is empty and <typeparamref name="TSource" /> is a nullable type, this method returns <see langword="null" />. If the source sequence is empty and <typeparamref name="TSource" /> is a non-nullable struct, such as a primitive type, an <see cref="T:System.InvalidOperationException" /> is thrown.</para>
+        <para>If the source sequence contains only values that are <see langword="null" />.</para></remarks>
         <exception cref="T:System.ArgumentNullException">
           <paramref name="source" /> is <see langword="null" />.</exception>
         <exception cref="T:System.ArgumentException">No key extracted from <paramref name="source" /> implements the <see cref="T:System.IComparable" /> or <see cref="T:System.IComparable`1" /> interface.</exception>
+        <exception cref="T:System.InvalidOperationException">
+          <typeparamref name="TSource" /> is a primitive type and the source sequence is empty.</exception>
       </Docs>
     </Member>
     <Member MemberName="OfType&lt;TResult&gt;">