ASP.NET Core ViewComponent调用：InvalidCastException

Question

Here is what I have

I have a view component as

public class TestViewComponent : ViewComponent
{
     public async Task<IViewComponentResult> InvokeAsync(int param1, int param2)
     {
         return Content(param1.ToString() + param2);
     }
}

And a controller as

public class HomeController : Controller
{
     private Dictionary<string, object> _dict = new Dictionary<string, object>();

     public IActionResult Index()
     {
         _dict = new Dictionary<string, object>() { ["param1"] = 100, ["param2"] = 200 };
         return ViewComponent("Test", _dict)
     }

     public IActionResult Index1()
     {
         var obj = new { param1 = 100, param2 = 200 };
         var objString = JsonConvert.SerializeObject(obj);
         _dict = JsonConvert.DeserializeObject<Dictionary<string, object>>(objString);
         return ViewComponent("Test", _dict);
     }
 }

When I call the first Index action everything is good. It works as expected but when I call the Index1 action I get an error with the following stack trace

System.InvalidCastException: Unable to cast object of type 'System.Int64' to type 'System.Int32'.
   at lambda_method(Closure , Object , Object[] )
   at Microsoft.AspNetCore.Mvc.ViewComponents.DefaultViewComponentInvoker.<InvokeAsyncCore>d__6.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.ViewComponents.DefaultViewComponentInvoker.<InvokeAsync>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.ViewComponents.DefaultViewComponentHelper.<InvokeCoreAsync>d__12.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.Internal.ViewComponentResultExecutor.<ExecuteAsync>d__6.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeResultAsync>d__30.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeNextResultFilterAsync>d__28.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ResultExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeNextResourceFilter>d__22.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ResourceExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeAsync>d__20.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Builder.RouterMiddleware.<Invoke>d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.<Invoke>d__6.MoveNext()

It seems there is some issue after the Deserialization. The exception is thrown even before the InvokeAsync method of the view component is called. I have been stuck on this for a while. Any help will be really appreciated. Thanks.

Answer 1

The error message is pretty much telling what's happening here. The actual object s in the deserialized dictionary are Int64 s, which the arguments expected by the ViewComponent are Int32 (also called int in C#).