Do not limit the error controller to a specific HTTP method

sandbox/OpenIddict.Sandbox.AspNetCore.Client/Controllers/ErrorController.cs

@@ -12,21 +12,20 @@ namespace OpenIddict.Sandbox.AspNetCore.Client;
 
 public class ErrorController : Controller
 {
-    [HttpGet, HttpPost, Route("~/error")]
+    [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true), Route("~/error")]
     public IActionResult Error()
     {
-        // If the error was not caused by an invalid
+        // If the error originated from the OpenIddict client, render the error details.
-        // OIDC request, display a generic error page.
         var response = HttpContext.GetOpenIddictClientResponse();
-        if (response is null)
+        if (response is not null)
         {
-            return View(new ErrorViewModel());
+            return View(new ErrorViewModel
+            {
+                Error = response.Error,
+                ErrorDescription = response.ErrorDescription
+            });
         }
 
-        return View(new ErrorViewModel
+        return View(new ErrorViewModel());
-        {
-            Error = response.Error,
-            ErrorDescription = response.ErrorDescription
-        });
     }
 }

sandbox/OpenIddict.Sandbox.AspNetCore.Server/Controllers/ErrorController.cs

@@ -12,21 +12,20 @@ namespace OpenIddict.Sandbox.AspNetCore.Server;
 
 public class ErrorController : Controller
 {
-    [HttpGet, HttpPost, Route("~/error")]
+    [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true), Route("~/error")]
     public IActionResult Error()
     {
-        // If the error was not caused by an invalid
+        // If the error originated from the OpenIddict server, render the error details.
-        // OIDC request, display a generic error page.
         var response = HttpContext.GetOpenIddictServerResponse();
-        if (response is null)
+        if (response is not null)
         {
-            return View(new ErrorViewModel());
+            return View(new ErrorViewModel
+            {
+                Error = response.Error,
+                ErrorDescription = response.ErrorDescription
+            });
         }
 
-        return View(new ErrorViewModel
+        return View(new ErrorViewModel());
-        {
-            Error = response.Error,
-            ErrorDescription = response.ErrorDescription
-        });
     }
 }

shared/OpenIddict.Extensions/OpenIddictHelpers.cs

@@ -1387,7 +1387,7 @@ internal static class OpenIddictHelpers
             {
                 foreach (var entry in _expandingAccumulator)
                 {
-                    _accumulator[entry.Key] = new StringValues(entry.Value.ToArray());
+                    _accumulator[entry.Key] = new StringValues([.. entry.Value]);
                 }
             }
 

src/OpenIddict.Abstractions/Primitives/OpenIddictExtensions.cs

@@ -660,7 +660,7 @@ public static class OpenIddictExtensions
                     }
                 }
 
-                builder.Add(group.Key, destinations.ToArray());
+                builder.Add(group.Key, [.. destinations]);
             }
         }
 
@@ -697,7 +697,7 @@ public static class OpenIddictExtensions
                     }
                 }
 
-                builder.Add(group.Key, destinations.ToArray());
+                builder.Add(group.Key, [.. destinations]);
             }
         }