DialogFactory is Null

Updated over 6 months ago

Environment

Product

Dialog for Blazor, RootComponent for Blazor

Description

The following exception may occur when calling the AlertAsync(), ConfirmAsync(), or PromptAsync() methods of the Telerik Blazor DialogFactory:

System.NullReferenceException: Object reference not set to an instance of an object

The following exception may occur on initial page load:

InvalidOperationException: Cannot provide a value for property '...' on type '...'. There is no registered service of type 'Telerik.Blazor.DialogFactory'

Cause

The null reference exception occurs if the DialogFactory CascadingParameter was not populated by the TelerikRootComponent. This in turn indicates one of the following:

• The TelerikRootComponent is missing in the Blazor app.
• The root component is present, but it's in the same .razor file as the DialogFactory cascading parameter.
• The Blazor app is using Per Page / Component Interactity Location and the root component is present, but it's in a static .razor component or layout.

The invalid operation exception occurs if the app tries to inject the DialogFactory as a dependency injection (service), which is not the intended way to use the predefined Telerik dialogs.

Solution

The following technical requirements ensure correct DialogFactory setup:

• Place a TelerikRootComponent in a layout .razor file in the app when using the application types below. If the DialogFactory must be avalable in the layout file itself, then place the TelerikRootComponent in a parent layout file.
  • Blazor Web App with Global Interactivity Location.
  • WebAssembly standalone app
  • Blazor Hybrid app
• When using a Blazor Web App with Per Page / Component Interactity Location, place the TelerikRootComponent inside an interactive Razor component, which is a parent of the component that consumes the DialogFactory.
• Always consume the DialogFactory as a [CascadingParameter], and not as a dependency injection with @inject.

See Also

• Predefined Blazor Dialogs
• TelerikRootComponent Overview