[release/2.2] Backport memory leak fix from 3.0

eng/PatchConfig.props

@@ -78,6 +78,7 @@ Later on, this will be checked using this condition:
   </PropertyGroup>
   <PropertyGroup Condition=" '$(VersionPrefix)' == '2.2.8' ">
     <PackagesInPatch>
+      Microsoft.AspNetCore.DataProtection.EntityFrameworkCore;
     </PackagesInPatch>
   </PropertyGroup>
 </Project>

src/DataProtection/EntityFrameworkCore/src/EntityFrameworkCoreXmlRepository.cs

@@ -42,8 +42,10 @@ public virtual IReadOnlyCollection<XElement> GetAllElements()
         {
             using (var scope = _services.CreateScope())
             {
-                var context = scope.ServiceProvider.GetRequiredService<TContext>();
-                return context.DataProtectionKeys.AsNoTracking().Select(key => TryParseKeyXml(key.Xml)).ToList().AsReadOnly();
+                var context = scope.ServiceProvider.GetRequiredService<TContext>();	
+                // Put logger in a local such that `this` isn't captured.
+                var logger = _logger;
+                return context.DataProtectionKeys.AsNoTracking().Select(key => TryParseKeyXml(key.Xml, logger)).ToList().AsReadOnly();
             }
         }
 
@@ -65,15 +67,15 @@ public void StoreElement(XElement element, string friendlyName)
             }
         }
 
-        private XElement TryParseKeyXml(string xml)
+        private static XElement TryParseKeyXml(string xml, ILogger logger)
         {
             try
             {
                 return XElement.Parse(xml);
             }
             catch (Exception e)
             {
-                _logger?.LogExceptionWhileParsingKeyXml(xml, e);
+                logger?.LogExceptionWhileParsingKeyXml(xml, e);
                 return null;
             }
         }