There is no validation in the JSON payload input box

[v-ruizh]

OS: Win10
Build Version: 20200827.4

Repro Steps:

1. Open a webapi project in VS Code.
2. F1 -> Dapr: Scaffold Dapr Tasks -> .NET Core Launch (web) -> Enter a Dapr ID 'app' for the application -> Enter the port '5000'.
3. Open the "Controllers/WeatherForecastController.cs" file.
4. Add the following within the class definition:

[HttpPost]
public ActionResult Post([FromBody] object body)
{
  return new JsonResult(body);
}

5. Switch to the debug tab and change the configuration to '.NET Core Launch (web) with Dapr', then F5.
6. F1 -> Dapr: Invoke (POST) Application Method -> Enter 'WeatherForecast' with the application method -> Enter an invalid JSON payload.

Expect:
There is an error when inputting the invalid JSON payload.

Actual:
There is no validation for the JSON payload input box.

More Info:
There is an error in notification when invoking application method.

[philliphoff]

@v-ruizh Agreed, while we do catch and report the error, it's not at the most convenient point (i.e. during input of the JSON).