Merge to Live

.github/copilot-instructions.md

@@ -1,7 +1,7 @@
 ---
 author: tdykstra
 ms.author: wpickett
-ms.date: 09-21-2025
+ms.date: 10-16-2025
 ---
 
 # Copilot Instructions for `dotnet/AspNetCore.Docs`
@@ -78,6 +78,7 @@ When working on an issue:
 
 ## Repository-Specific Guidelines
 - [ ] Follow the [Microsoft Writing Style Guide](https://learn.microsoft.com/en-us/style-guide/welcome/)
+  - [ ] Use contractions following the guidance in [Use contractions](https://learn.microsoft.com/en-us/style-guide/word-choice/use-contractions)
 - [ ] **Repository Exceptions**:
   - [ ] Number ordered lists as "1." for every item (don't use sequential numbers)
   - [ ] Use backticks around content specifically for file names (`file.txt`), folders (`folder`), file paths (`folder/file.txt`), custom types (`myVariable`, `MyClass`), raw URLs in the text (`https://www.contoso.com`), URL segments (`/product/id/199`), file extensions (`.razor`), NuGet packages (`Microsoft.AspNetCore.SignalR.Client`), and code that should never be localized

aspnetcore/data/ef-rp/intro/samples/cu-completed-stages/part7/ContosoUniversity/Pages/Courses/Create.cshtml.cs

@@ -43,7 +43,7 @@ public async Task<IActionResult> OnPostAsync()
                 return RedirectToPage("./Index");
             }
 
-            // Select DepartmentID if TryUpdateModelAsync fails.
+            // Repopulate departments dropdown. emptyCourse.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, emptyCourse.DepartmentID);
             return Page();
         }

aspnetcore/data/ef-rp/intro/samples/cu-completed-stages/part7/ContosoUniversity/Pages/Courses/Edit.cshtml.cs

@@ -32,7 +32,7 @@ public async Task<IActionResult> OnGetAsync(int? id)
                 return NotFound();
             }
 
-            // Select current DepartmentID.
+            // Populate departments dropdown. Course.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, Course.DepartmentID);
             return Page();
         }
@@ -60,7 +60,7 @@ public async Task<IActionResult> OnPostAsync(int? id)
                 return RedirectToPage("./Index");
             }
 
-            // Select DepartmentID if TryUpdateModelAsync fails.
+            // Repopulate departments dropdown. courseToUpdate.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, courseToUpdate.DepartmentID);
             return Page();
         }

aspnetcore/data/ef-rp/intro/samples/cu/Pages/Courses/Create.cshtml.cs

@@ -41,7 +41,7 @@ public async Task<IActionResult> OnPostAsync()
                 return RedirectToPage("./Index");
             }
 
-            // Select DepartmentID if TryUpdateModelAsync fails.
+            // Repopulate departments dropdown. emptyCourse.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, emptyCourse.DepartmentID);
             return Page();
         }

aspnetcore/data/ef-rp/intro/samples/cu/Pages/Courses/Edit.cshtml.cs

@@ -32,7 +32,7 @@ public async Task<IActionResult> OnGetAsync(int? id)
                 return NotFound();
             }
 
-            // Select current DepartmentID.
+            // Populate departments dropdown. Course.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context,Course.DepartmentID);
             return Page();
         }
@@ -55,7 +55,7 @@ public async Task<IActionResult> OnPostAsync(int? id)
                 return RedirectToPage("./Index");
             }
 
-            // Select DepartmentID if TryUpdateModelAsync fails.
+            // Repopulate departments dropdown. courseToUpdate.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, courseToUpdate.DepartmentID);
             return Page();
         }       

aspnetcore/data/ef-rp/intro/samples/cu20snapshots/cu-part7/Pages/Courses/Create.cshtml.cs

@@ -53,7 +53,7 @@ public async Task<IActionResult> OnPostAsync()
                 return RedirectToPage("./Index");
             }
 
-            // Select DepartmentID if TryUpdateModelAsync fails.
+            // Repopulate departments dropdown. emptyCourse.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, emptyCourse.DepartmentID);
             return Page();
         }

aspnetcore/data/ef-rp/intro/samples/cu20snapshots/cu-part7/Pages/Courses/Edit.cshtml.cs

@@ -38,7 +38,7 @@ public async Task<IActionResult> OnGetAsync(int? id)
                 return NotFound();
             }
 
-            // Select current DepartmentID.
+            // Populate departments dropdown. Course.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, Course.DepartmentID);
             return Page();
         }
@@ -61,7 +61,7 @@ public async Task<IActionResult> OnPostAsync(int? id)
                 return RedirectToPage("./Index");
             }
 
-            // Select DepartmentID if TryUpdateModelAsync fails.
+            // Repopulate departments dropdown. courseToUpdate.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, courseToUpdate.DepartmentID);
             return Page();
         }

aspnetcore/data/ef-rp/intro/samples/cu20snapshots/cu-part8/Pages/Courses/Create.cshtml.cs

@@ -53,7 +53,7 @@ public async Task<IActionResult> OnPostAsync()
                 return RedirectToPage("./Index");
             }
 
-            // Select DepartmentID if TryUpdateModelAsync fails.
+            // Repopulate departments dropdown. emptyCourse.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, emptyCourse.DepartmentID);
             return Page();
         }

aspnetcore/data/ef-rp/intro/samples/cu20snapshots/cu-part8/Pages/Courses/Edit.cshtml.cs

@@ -38,7 +38,7 @@ public async Task<IActionResult> OnGetAsync(int? id)
                 return NotFound();
             }
 
-            // Select current DepartmentID.
+            // Populate departments dropdown. Course.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, Course.DepartmentID);
             return Page();
         }
@@ -61,7 +61,7 @@ public async Task<IActionResult> OnPostAsync(int? id)
                 return RedirectToPage("./Index");
             }
 
-            // Select DepartmentID if TryUpdateModelAsync fails.
+            // Repopulate departments dropdown. courseToUpdate.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, courseToUpdate.DepartmentID);
             return Page();
         }

aspnetcore/data/ef-rp/intro/samples/cu30/Pages/Courses/Create.cshtml.cs

@@ -36,7 +36,7 @@ public async Task<IActionResult> OnPostAsync()
                 return RedirectToPage("./Index");
             }
 
-            // Select DepartmentID if TryUpdateModelAsync fails.
+            // Repopulate departments dropdown. emptyCourse.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, emptyCourse.DepartmentID);
             return Page();
         }

aspnetcore/data/ef-rp/intro/samples/cu30/Pages/Courses/Edit.cshtml.cs

@@ -32,7 +32,7 @@ public async Task<IActionResult> OnGetAsync(int? id)
                 return NotFound();
             }
 
-            // Select current DepartmentID.
+            // Populate departments dropdown. Course.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, Course.DepartmentID);
             return Page();
         }
@@ -60,7 +60,7 @@ public async Task<IActionResult> OnPostAsync(int? id)
                 return RedirectToPage("./Index");
             }
 
-            // Select DepartmentID if TryUpdateModelAsync fails.
+            // Repopulate departments dropdown. courseToUpdate.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, courseToUpdate.DepartmentID);
             return Page();
         }       

aspnetcore/data/ef-rp/intro/samples/cu50/Pages/Courses/Create.cshtml.cs

@@ -36,7 +36,7 @@ public async Task<IActionResult> OnPostAsync()
                 return RedirectToPage("./Index");
             }
 
-            // Select DepartmentID if TryUpdateModelAsync fails.
+            // Repopulate departments dropdown. emptyCourse.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, emptyCourse.DepartmentID);
             return Page();
         }

aspnetcore/data/ef-rp/intro/samples/cu50/Pages/Courses/Edit.cshtml.cs

@@ -32,7 +32,7 @@ public async Task<IActionResult> OnGetAsync(int? id)
                 return NotFound();
             }
 
-            // Select current DepartmentID.
+            // Populate departments dropdown. Course.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, Course.DepartmentID);
             return Page();
         }
@@ -60,7 +60,7 @@ public async Task<IActionResult> OnPostAsync(int? id)
                 return RedirectToPage("./Index");
             }
 
-            // Select DepartmentID if TryUpdateModelAsync fails.
+            // Repopulate departments dropdown. courseToUpdate.DepartmentID determines the selected item.
             PopulateDepartmentsDropDownList(_context, courseToUpdate.DepartmentID);
             return Page();
         }       

aspnetcore/data/ef-rp/update-related-data.md

@@ -30,8 +30,10 @@ Create a `Pages/Courses/DepartmentNamePageModel.cs` file with the following code
 
 [!code-csharp[](intro/samples/cu50/Pages/Courses/DepartmentNamePageModel.cs)]
 
-The preceding code creates a <xref:Microsoft.AspNetCore.Mvc.Rendering.SelectList> to contain the list of department names. If `selectedDepartment` is specified, that department is selected in the `SelectList`.
+The preceding code creates a <xref:Microsoft.AspNetCore.Mvc.Rendering.SelectList> to contain the list of department names. The `selectedDepartment` parameter allows the calling code to specify the item that will be selected when the drop-down list is rendered. However, when using the Select Tag Helper with `asp-for`, the selected item is determined by the model property value (such as `Course.DepartmentID`), not by the `selectedDepartment` parameter.
 
+> [!IMPORTANT]
+> When using the Select Tag Helper with `asp-for="Course.DepartmentID"`, the selected option is automatically determined by the value of `Course.DepartmentID`. The `selectedDepartment` parameter passed to the SelectList constructor is ignored in this scenario.
 The Create and Edit page model classes will derive from `DepartmentNamePageModel`.
 
 ### Update the Course Create page model
@@ -77,7 +79,7 @@ Update `Pages/Courses/Edit.cshtml.cs` with the following code:
 
 [!code-csharp[](intro/samples/cu50/Pages/Courses/Edit.cshtml.cs?highlight=8,28,35,36,40-66)]
 
-The changes are similar to those made in the Create page model. In the preceding code, `PopulateDepartmentsDropDownList` passes in the department ID, which selects that department in the drop-down list.
+The changes are similar to those made in the Create page model. In the preceding code, `PopulateDepartmentsDropDownList` passes in the department ID. When using the Select Tag Helper with `asp-for="Course.DepartmentID"`, the selected item in the drop-down list is determined by the value of `Course.DepartmentID`, not by the `selectedDepartment` parameter passed to the SelectList constructor.
 
 ### Update the Course Edit Razor page
 
@@ -253,7 +255,7 @@ Create a `Pages/Courses/DepartmentNamePageModel.cs` file with the following code
 
 [!code-csharp[](intro/samples/cu30/Pages/Courses/DepartmentNamePageModel.cs)]
 
-The preceding code creates a <xref:Microsoft.AspNetCore.Mvc.Rendering.SelectList> to contain the list of department names. If `selectedDepartment` is specified, that department is selected in the `SelectList`.
+The preceding code creates a <xref:Microsoft.AspNetCore.Mvc.Rendering.SelectList> to contain the list of department names. The `selectedDepartment` parameter allows the calling code to specify the item that will be selected when the drop-down list is rendered. However, when using the Select Tag Helper with `asp-for`, the selected item is determined by the model property value (such as `Course.DepartmentID`), not by the `selectedDepartment` parameter.
 
 The Create and Edit page model classes will derive from `DepartmentNamePageModel`.
 
@@ -300,7 +302,7 @@ Update `Pages/Courses/Edit.cshtml.cs` with the following code:
 
 [!code-csharp[](intro/samples/cu30/Pages/Courses/Edit.cshtml.cs?highlight=8,28,35,36,40-66)]
 
-The changes are similar to those made in the Create page model. In the preceding code, `PopulateDepartmentsDropDownList` passes in the department ID, which selects that department in the drop-down list.
+The changes are similar to those made in the Create page model. In the preceding code, `PopulateDepartmentsDropDownList` passes in the department ID. When using the Select Tag Helper with `asp-for="Course.DepartmentID"`, the selected item in the drop-down list is determined by the value of `Course.DepartmentID`, not by the `selectedDepartment` parameter passed to the SelectList constructor.
 
 ### Update the Course Edit Razor page
 
@@ -470,7 +472,7 @@ The Courses/Create and Courses/Edit pages each need a list of department names.
 
 [!code-csharp[](intro/samples/cu/Pages/Courses/DepartmentNamePageModel.cshtml.cs?highlight=9,11,20-21)]
 
-The preceding code creates a <xref:Microsoft.AspNetCore.Mvc.Rendering.SelectList> to contain the list of department names. If `selectedDepartment` is specified, that department is selected in the `SelectList`.
+The preceding code creates a <xref:Microsoft.AspNetCore.Mvc.Rendering.SelectList> to contain the list of department names. The `selectedDepartment` parameter allows the calling code to specify the item that will be selected when the drop-down list is rendered. However, when using the Select Tag Helper with `asp-for`, the selected item is determined by the model property value (such as `Course.DepartmentID`), not by the `selectedDepartment` parameter.
 
 The Create and Edit page model classes will derive from `DepartmentNamePageModel`.
 
@@ -517,7 +519,7 @@ Replace the code in `Pages/Courses/Edit.cshtml.cs` with the following code:
 
 [!code-csharp[](intro/samples/cu/Pages/Courses/Edit.cshtml.cs?highlight=8,28,35,36,40,47-999)]
 
-The changes are similar to those made in the Create page model. In the preceding code, `PopulateDepartmentsDropDownList` passes in the department ID, which select the department specified in the drop-down list.
+The changes are similar to those made in the Create page model. In the preceding code, `PopulateDepartmentsDropDownList` passes in the department ID. When using the Select Tag Helper with `asp-for="Course.DepartmentID"`, the selected item in the drop-down list is determined by the value of `Course.DepartmentID`, not by the `selectedDepartment` parameter passed to the SelectList constructor.
 
 Update `Pages/Courses/Edit.cshtml` with the following markup:
 

aspnetcore/fundamentals/host/platform-specific-configuration.md

@@ -5,7 +5,7 @@ description: Discover how to enhance an ASP.NET Core app from an external assemb
 monikerRange: '>= aspnetcore-2.1'
 ms.author: tdykstra
 ms.custom: mvc
-ms.date: 09/26/2019
+ms.date: 09/04/2025
 uid: fundamentals/configuration/platform-specific-configuration
 ---
 # Use hosting startup assemblies in ASP.NET Core
@@ -336,6 +336,9 @@ deployment/additionalDeps/shared/Microsoft.AspNetCore.App/3.0.0/StartupDiagnosti
 
 For runtime to discover the runtime store location, the additional dependencies file location is added to the `DOTNET_ADDITIONAL_DEPS` environment variable.
 
+> [!NOTE]
+> The `DOTNET_ADDITIONAL_DEPS` environment variable only works with framework-dependent applications. This environment variable is ignored for self-contained applications.
+
 In the sample app (*RuntimeStore* project), building the runtime store and generating the additional dependencies file is accomplished using a [PowerShell](/powershell/scripting/overview) script.
 
 For examples of how to set environment variables for various operating systems, see [Use multiple environments](xref:fundamentals/environments).
@@ -722,6 +725,9 @@ deployment/additionalDeps/shared/Microsoft.AspNetCore.App/2.1.0/StartupDiagnosti
 
 For runtime to discover the runtime store location, the additional dependencies file location is added to the `DOTNET_ADDITIONAL_DEPS` environment variable.
 
+> [!NOTE]
+> The `DOTNET_ADDITIONAL_DEPS` environment variable only works with framework-dependent applications. This environment variable is ignored for self-contained applications.
+
 In the sample app (*RuntimeStore* project), building the runtime store and generating the additional dependencies file is accomplished using a [PowerShell](/powershell/scripting/overview) script.
 
 For examples of how to set environment variables for various operating systems, see [Use multiple environments](xref:fundamentals/environments).

aspnetcore/fundamentals/openapi/customize-openapi.md

@@ -102,6 +102,14 @@ For example, the following operation transformer adds `500` as a response status
 
 [!code-csharp[](~/fundamentals/openapi/samples/10.x/WebMinOpenApi/Program.cs?name=snippet_operationtransformer1)]
 
+<!-- UPDATE 10.0 - API doc cross-link:
+                   <xref:Microsoft.AspNetCore.Http.OpenApiRouteHandlerBuilderExtensions.AddOpenApiOperationTransformer%2A>
+-->
+
+Operation transformers can also be added to specific endpoint with the `AddOpenApiOperationTransformer` API, instead of all endpoints in a document. This can be useful to change specific OpenAPI data for a specific endpoint, like adding a security scheme, response description or other OpenAPI operation properties. The following example demonstrates adding an operation transformer to a deprecated endpoint specifically, which marks the endpoint as deprecated in the OpenAPI document.
+
+[!code-csharp[](~/fundamentals/openapi/samples/10.x/WebMinOpenApi/Program.cs?name=snippet_operationtransformer2)]
+
 ## Use schema transformers
 
 Schemas are the data models that are used in request and response bodies in an OpenAPI document. Schema transformers are useful when a modification: