Remove a couple LINQ usages in Microsoft.Extensions (#47873)

* Remove a couple LINQ usages in Microsoft.Extensions

* Respond to PR feedback.

Author: eerhardt

src/libraries/Microsoft.Extensions.Configuration.Xml/src/XmlStreamConfigurationProvider.cs

@@ -68,7 +68,7 @@ public static IDictionary<string, string> Read(Stream stream, XmlDocumentDecrypt
                             break;
 
                         case XmlNodeType.EndElement:
-                            if (prefixStack.Any())
+                            if (prefixStack.Count != 0)
                             {
                                 // If this EndElement node comes right after an Element node,
                                 // it means there is no text/CDATA node in current element
@@ -179,7 +179,7 @@ private static void AddNamePrefix(XmlReader reader, Stack<string> prefixStack,
             }
 
             // If current element is not root element
-            if (prefixStack.Any())
+            if (prefixStack.Count != 0)
             {
                 string lastPrefix = prefixStack.Pop();
                 prefixStack.Push(ConfigurationPath.Combine(lastPrefix, reader.Value));

src/libraries/Microsoft.Extensions.Logging.Abstractions/src/LogValuesFormatter.cs

@@ -4,7 +4,6 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Linq;
 using System.Globalization;
 using System.Text;
 
@@ -202,10 +201,21 @@ private object FormatArgument(object? value)
             }
 
             // if the value implements IEnumerable, build a comma separated string.
-            var enumerable = value as IEnumerable;
-            if (enumerable != null)
+            if (value is IEnumerable enumerable)
             {
-                return string.Join(", ", enumerable.Cast<object>().Select(o => o ?? NullValue));
+                var vsb = new ValueStringBuilder(stackalloc char[256]);
+                bool first = true;
+                foreach (object e in enumerable)
+                {
+                    if (!first)
+                    {
+                        vsb.Append(", ");
+                    }
+
+                    vsb.Append(e != null ? e.ToString() : NullValue);
+                    first = false;
+                }
+                return vsb.ToString();
             }
 
             return value;