dotnet type_error ai_generated true

System.InvalidOperationException: The model item passed into the ViewDataDictionary is of type 'X', but this ViewDataDictionary instance requires a model item of type 'Y'.

ID: dotnet/razor-page-view-data-dictionary

Also available as: JSON · Markdown · 中文
95%Fix Rate
88%Confidence
1Evidence
2023-03-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
.NET 6.0 active — — —
.NET 7.0 active — — —
.NET 8.0 active — — —
ASP.NET Core 6.0 active — — —
ASP.NET Core 7.0 active — — —
ASP.NET Core 8.0 active — — —

Root Cause

ASP.NET Core Razor Page or View expects a strongly-typed model of type Y, but the controller or page handler passes a model of type X, causing a type mismatch in ViewDataDictionary.

generic

中文

ASP.NET Core Razor 页面或视图期望类型为 Y 的强类型模型，但控制器或页面处理程序传递了类型为 X 的模型，导致 ViewDataDictionary 中的类型不匹配。

Official Documentation

https://learn.microsoft.com/en-us/aspnet/core/mvc/views/overview

Workarounds

  1. 95% success Ensure the controller action returns a ViewResult with the correct model type: return View(modelOfTypeY); where modelOfTypeY is of the type declared in the view's @model directive. 
    Ensure the controller action returns a ViewResult with the correct model type: return View(modelOfTypeY); where modelOfTypeY is of the type declared in the view's @model directive.
  2. 85% success If the view must accept multiple types, change the @model directive to a base class or interface that both X and Y implement, then adjust the view accordingly. 
    If the view must accept multiple types, change the @model directive to a base class or interface that both X and Y implement, then adjust the view accordingly.
  3. 90% success Use a ViewModel that contains both X and Y as properties, and pass that ViewModel to the view. 
    Use a ViewModel that contains both X and Y as properties, and pass that ViewModel to the view.

中文步骤

  1. 确保控制器操作返回正确模型类型的 ViewResult：return View(modelOfTypeY); 其中 modelOfTypeY 的类型与视图的 @model 指令声明的类型一致。
  2. 如果视图必须接受多种类型，将 @model 指令改为 X 和 Y 都实现的基类或接口，然后相应调整视图。
  3. 使用包含 X 和 Y 作为属性的 ViewModel，并将该 ViewModel 传递给视图。

Dead Ends

Common approaches that don't work:

  1. Change the @model directive in the view to match the passed type X 85% fail

    This breaks the view's contract with its expected model type; the view may use properties of Y that don't exist on X, causing runtime errors.

  2. Use ViewBag or ViewData to pass the model instead of a strongly-typed model 70% fail

    This defeats the purpose of strongly-typed views and can lead to runtime casting errors and loss of IntelliSense.

  3. Cast the model to type Y in the controller 90% fail

    If X and Y are unrelated types, casting will throw InvalidCastException at runtime.