diff --git a/src/Http/Routing/src/CompositeEndpointDataSource.cs b/src/Http/Routing/src/CompositeEndpointDataSource.cs
index e6b1c0a19a..008ad09a9c 100644
--- a/src/Http/Routing/src/CompositeEndpointDataSource.cs
+++ b/src/Http/Routing/src/CompositeEndpointDataSource.cs
@@ -165,7 +165,7 @@ namespace Microsoft.AspNetCore.Routing
                         template = string.IsNullOrEmpty(template) ? "\"\"" : template;
                         sb.Append(template);
                         sb.Append(", Defaults: new { ");
-                        sb.Append(string.Join(", ", FormatValues(routeEndpoint.RoutePattern.Defaults)));
+                        sb.AppendJoin(", ", FormatValues(routeEndpoint.RoutePattern.Defaults));
                         sb.Append(" }");
                         var routeNameMetadata = routeEndpoint.Metadata.GetMetadata<IRouteNameMetadata>();
                         sb.Append(", Route Name: ");
@@ -174,7 +174,7 @@ namespace Microsoft.AspNetCore.Routing
                         if (routeValues.Count > 0)
                         {
                             sb.Append(", Required Values: new { ");
-                            sb.Append(string.Join(", ", FormatValues(routeValues)));
+                            sb.AppendJoin(", ", FormatValues(routeValues));
                             sb.Append(" }");
                         }
                         sb.Append(", Order: ");
@@ -184,7 +184,7 @@ namespace Microsoft.AspNetCore.Routing
                         if (httpMethodMetadata != null)
                         {
                             sb.Append(", Http Methods: ");
-                            sb.Append(string.Join(", ", httpMethodMetadata.HttpMethods));
+                            sb.AppendJoin(", ", httpMethodMetadata.HttpMethods);
                         }
                         sb.Append(", Display Name: ");
                         sb.Append(routeEndpoint.DisplayName);
diff --git a/src/Http/Routing/src/Matching/DfaNode.cs b/src/Http/Routing/src/Matching/DfaNode.cs
index f3f916b8e5..602a48a0e2 100644
--- a/src/Http/Routing/src/Matching/DfaNode.cs
+++ b/src/Http/Routing/src/Matching/DfaNode.cs
@@ -121,7 +121,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
             builder.Append(" c: ");
             if (Literals != null)
             {
-                builder.Append(string.Join(", ", Literals.Select(kvp => $"{kvp.Key}->({FormatNode(kvp.Value)})")));
+                builder.AppendJoin(", ", Literals.Select(kvp => $"{kvp.Key}->({FormatNode(kvp.Value)})"));
             }
             return builder.ToString();
             
diff --git a/src/Http/Routing/src/Matching/DictionaryJumpTable.cs b/src/Http/Routing/src/Matching/DictionaryJumpTable.cs
index 27445737e9..644f9c95ac 100644
--- a/src/Http/Routing/src/Matching/DictionaryJumpTable.cs
+++ b/src/Http/Routing/src/Matching/DictionaryJumpTable.cs
@@ -50,7 +50,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
             var builder = new StringBuilder();
             builder.Append("{ ");
 
-            builder.Append(string.Join(", ", _dictionary.Select(kvp => $"{kvp.Key}: {kvp.Value}")));
+            builder.AppendJoin(", ", _dictionary.Select(kvp => $"{kvp.Key}: {kvp.Value}"));
 
             builder.Append("$+: ");
             builder.Append(_defaultDestination);
diff --git a/src/Http/Routing/src/Matching/LinearSearchJumpTable.cs b/src/Http/Routing/src/Matching/LinearSearchJumpTable.cs
index 58f8b3d01d..37d5805c63 100644
--- a/src/Http/Routing/src/Matching/LinearSearchJumpTable.cs
+++ b/src/Http/Routing/src/Matching/LinearSearchJumpTable.cs
@@ -55,7 +55,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
             var builder = new StringBuilder();
             builder.Append("{ ");
 
-            builder.Append(string.Join(", ", _entries.Select(e => $"{e.text}: {e.destination}")));
+            builder.AppendJoin(", ", _entries.Select(e => $"{e.text}: {e.destination}"));
 
             builder.Append("$+: ");
             builder.Append(_defaultDestination);
diff --git a/src/Http/Routing/src/Tree/LinkGenerationDecisionTree.cs b/src/Http/Routing/src/Tree/LinkGenerationDecisionTree.cs
index 568c377745..6aa8b84867 100644
--- a/src/Http/Routing/src/Tree/LinkGenerationDecisionTree.cs
+++ b/src/Http/Routing/src/Tree/LinkGenerationDecisionTree.cs
@@ -248,7 +248,7 @@ namespace Microsoft.AspNetCore.Routing.Tree
                 }
                 sb.Append(matchesSb.ToString());
                 sb.Append(" (Matches: ");
-                sb.Append(string.Join(", ", node.Matches.Select(m => m.Entry.RouteTemplate.TemplateText)));
+                sb.AppendJoin(", ", node.Matches.Select(m => m.Entry.RouteTemplate.TemplateText));
                 sb.AppendLine(")");
             }
 
diff --git a/src/Middleware/CORS/src/Infrastructure/CorsPolicy.cs b/src/Middleware/CORS/src/Infrastructure/CorsPolicy.cs
index f541863c69..8c7529d30e 100644
--- a/src/Middleware/CORS/src/Infrastructure/CorsPolicy.cs
+++ b/src/Middleware/CORS/src/Infrastructure/CorsPolicy.cs
@@ -142,16 +142,16 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
             builder.Append(", SupportsCredentials: ");
             builder.Append(SupportsCredentials);
             builder.Append(", Origins: {");
-            builder.Append(string.Join(",", Origins));
+            builder.AppendJoin(",", Origins);
             builder.Append("}");
             builder.Append(", Methods: {");
-            builder.Append(string.Join(",", Methods));
+            builder.AppendJoin(",", Methods);
             builder.Append("}");
             builder.Append(", Headers: {");
-            builder.Append(string.Join(",", Headers));
+            builder.AppendJoin(",", Headers);
             builder.Append("}");
             builder.Append(", ExposedHeaders: {");
-            builder.Append(string.Join(",", ExposedHeaders));
+            builder.AppendJoin(",", ExposedHeaders);
             builder.Append("}");
             return builder.ToString();
         }
@@ -161,4 +161,4 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
             return Origins.Contains(origin, StringComparer.Ordinal);
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/Middleware/CORS/src/Infrastructure/CorsResult.cs b/src/Middleware/CORS/src/Infrastructure/CorsResult.cs
index 558a99a31d..16cf9bb66a 100644
--- a/src/Middleware/CORS/src/Infrastructure/CorsResult.cs
+++ b/src/Middleware/CORS/src/Infrastructure/CorsResult.cs
@@ -91,15 +91,15 @@ namespace Microsoft.AspNetCore.Cors.Infrastructure
             builder.Append(", AllowOrigin: ");
             builder.Append(AllowedOrigin);
             builder.Append(", AllowExposedHeaders: {");
-            builder.Append(string.Join(",", AllowedExposedHeaders));
+            builder.AppendJoin(",", AllowedExposedHeaders);
             builder.Append("}");
             builder.Append(", AllowHeaders: {");
-            builder.Append(string.Join(",", AllowedHeaders));
+            builder.AppendJoin(",", AllowedHeaders);
             builder.Append("}");
             builder.Append(", AllowMethods: {");
-            builder.Append(string.Join(",", AllowedMethods));
+            builder.AppendJoin(",", AllowedMethods);
             builder.Append("}");
             return builder.ToString();
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/Shared/StackTrace/StackFrame/MethodDisplayInfo.cs b/src/Shared/StackTrace/StackFrame/MethodDisplayInfo.cs
index b1c0ccc188..8079f96072 100644
--- a/src/Shared/StackTrace/StackFrame/MethodDisplayInfo.cs
+++ b/src/Shared/StackTrace/StackFrame/MethodDisplayInfo.cs
@@ -33,7 +33,7 @@ namespace Microsoft.Extensions.StackTrace.Sources
             builder.Append(GenericArguments);
 
             builder.Append("(");
-            builder.Append(string.Join(", ", Parameters.Select(p => p.ToString())));
+            builder.AppendJoin(", ", Parameters.Select(p => p.ToString()));
             builder.Append(")");
 
             if (!string.IsNullOrEmpty(SubMethod))