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WinForms Inline AI Assistant Properties, Methods, and Events

Updated on Nov 11, 2026

The Telerik UI for WinForms RadInlineAIAssistant API configures the popup, connects it to a text control, and manages the request and response lifecycle. The component raises PromptRequest; your application supplies the AI service integration.

Property	Description
`Commands`	Gets the collection of commands and command groups shown in the dropdown. Add entries to the collection; do not replace the collection itself.
`NullText`	Gets or sets the prompt placeholder. The default localization provider supplies "Ask AI anything...".
`PopupWidth`	Gets or sets the popup width in logical pixels. Defaults to `460`; values below `100` are clamped to `100`. The width is applied when the popup opens.
`ResponseMaxHeight`	Gets or sets the maximum height of the scrollable response area in pixels. Defaults to `250`. Changing it updates the layout of an open popup.
`ThemeName`	Inherited from `RadComponent`. Sets the popup theme. When unset, the assistant uses the attached `RadControl` host's theme when opening.
`OpeningEventName`	Gets or sets the name of a public instance event on the attached control that opens the assistant. Defaults to `null`. The event must have a compatible handler signature; missing or incompatible events are ignored.
`AutoCloseOnFocusLost`	Gets or sets whether the popup closes when another application is activated. Defaults to `true`. This setting does not disable all other closing triggers.
`AutoCloseOnHostChanged`	Gets or sets whether host size changes and provider-reported viewport changes close the popup. Defaults to `true`. Movement or resizing of the containing form still requests a close regardless of this setting.
`InteractionProvider`	Gets or sets the `IInlineAIAssistantInteractionProvider` that supplies host text, anchor coordinates, and editing operations. Not exposed in the designer.
`AttachedControl`	Gets the control passed to `AttachTo`. Read-only.
`Popup`	Gets the `InlineAIAssistantPopup` instance. Read-only and hidden from designer serialization.
`InlineAIAssistantElement`	Gets the root `RadInlineAIAssistantElement` for access to the assistant's element hierarchy. Read-only.

The popup also uses the host's right-to-left layout when it opens.

Response and State Properties

Property	Description
`IsOpen`	Gets whether the popup is currently open. Read-only; use `Show` and `Close` to change visibility.
`IsProcessing`	Gets or sets the element's processing state. Setting this property is not a substitute for starting or canceling a request through the request methods.
`ResponseText`	Gets or sets the response text. Setting it cancels the current request. A nonempty value displays a completed response; a null or empty value clears the response and returns the element to its idle state.

For asynchronous requests, use the PromptRequest event data's SetResponse, AppendResponse, CompleteResponse, and FailResponse methods instead of assigning ResponseText. These methods retain the originating request's identity and reject stale updates.

Method	Description
`AttachTo(Control host)`	Attaches the assistant to a host. Creates a built-in provider for `TextBoxBase`, `RadTextBox`, or `RadTextBoxControl` when no provider is assigned. Passing `null` throws `ArgumentNullException`.
`Detach()`	Detaches from the current host, requests that the popup close, and releases a provider owned by the assistant.
`Show()`	Opens at the anchor reported by the provider. Does nothing when no provider exists or the provider cannot supply a visible anchor.
`Show(Rectangle screenAnchor)`	Opens at an explicit rectangle in screen coordinates. A provider is still required to apply responses to a host.
`Close()`	Requests that the popup close. A `Closing` handler can cancel the close.
`ClearResponse()`	Clears the response text and hides the response area. This method does not cancel an active request; use `CancelRequest` when necessary.

Both Show overloads do nothing if the assistant is already open or disposed. For RadRichTextEditor, assign the editor's InlineAIAssistant property to attach the component and configure the editor-specific provider.

Request and Response Methods

Method	Description
`SubmitPrompt(string prompt)`	Cancels any previous request, clears its response, enters the processing state, and raises `PromptRequest`.
`AppendResponse(string chunk)`	Appends a chunk to the current active request. Does not complete the request.
`CompleteResponse()`	Marks the current active request as complete and updates the available response actions.
`FailResponse(Exception error)`	Fails the current active request and displays a localized generic error. The exception message is not displayed.
`CancelRequest()`	Cancels the current request token and exits processing. It does not close the popup or discard text already received.
`CanInsert()`	Asks the interaction provider whether it can insert the current response.
`CanReplace()`	Asks the interaction provider whether it can replace the selection with the current response.
`Insert()`	Applies the response through the provider and requests that the popup close.
`Replace()`	Replaces the selection through the provider and requests that the popup close.
`Discard()`	Cancels the request, clears the response, and returns focus to the prompt without closing the popup.

AppendResponse, CompleteResponse, and FailResponse also have overloads that take the CancellationToken from the request event. Use these overloads, or the corresponding event-data methods, when work can outlive a request. The tokenless overloads target whichever request is current when called.

Call setup, opening, and prompt-submission APIs on the UI thread. The response-delivery methods support asynchronous callbacks and marshal updates through the synchronization context captured when the request starts.

Insert and Replace require the element to be in its response state and the provider to allow the operation. Error text and text still being generated cannot be applied through these methods. Canceling a request can leave received text available as a response.

Events

The component exposes .NET events for popup visibility, prompt requests, command submission, and response actions. For cancelable events, set Cancel to true to prevent the operation.

Event	Event data	Description
`Opening`	`InlineAIAssistantOpeningEventArgs`	Raised before opening. Provides read-only `Host`, `AnchorRectangle`, and `SelectedText`. Set `Cancel` to keep the popup closed.
`Opened`	`EventArgs`	Raised after the popup opens.
`Closing`	`RadPopupClosingEventArgs`	Raised before an allowed close operation. Inspect `CloseReason` and set `Cancel` to keep the popup open.
`Closed`	`RadPopupClosedEventArgs`	Raised after closing. The assistant cancels the current request before raising this event. Closing does not automatically clear the response.
`PromptRequest`	`InlineAIAssistantPromptRequestEventArgs`	Raised when the user submits a prompt, selects a command, or the application calls `SubmitPrompt`. Supply the response through the event data.
`CommandExecuting`	`InlineAIAssistantCommandEventArgs`	Raised before a selected command submits its prompt. Modify `Prompt` or set `Cancel` to prevent submission.
`ResponseActionExecuting`	`InlineAIAssistantResponseActionEventArgs`	Raised before Insert, Replace, or Discard. Inspect `Action`, modify `ResponseText`, or set `Cancel` to skip the action.
`ResponseActionExecuted`	`InlineAIAssistantResponseActionEventArgs`	Raised after the response action is applied. For Insert and Replace, this occurs before the subsequent close request.

Handling Prompt Requests

PromptRequest provides an InlineAIAssistantPromptRequestEventArgs instance with the following members:

Member	Description
`Prompt`	The submitted instruction.
`SelectedText`	The host selection captured when the request starts.
`FullText`	The full host text, computed on first access. Read it on the UI thread.
`Command`	The command that submitted the prompt, or `null` for a free-form prompt.
`CancellationToken`	The token for stopping asynchronous service work.
`SetResponse(string)`	Displays the complete response and ends processing.
`AppendResponse(string)`	Appends a chunk to the current request's response.
`CompleteResponse()`	Marks a streamed response as complete.
`FailResponse(Exception)`	Ends processing and displays a localized generic error.

The event-data methods retain the originating request identity and ignore stale updates. They support asynchronous handlers, including SetResponse after an await. See Handling Responses for complete examples.

Opening applies to the component's Show methods, including calls made through an attached host event. The IsOpen property is read-only; use Show and Close to change popup visibility.

The following example allows opening only when text is selected. It assumes an existing assistant field and the Telerik.WinControls.UI namespace.

Registering the opening handler

C#
this.assistant.Opening += this.OnAssistantOpening;
VB.NET
AddHandler Me.assistant.Opening, AddressOf Me.OnAssistantOpening

Requiring a selection

C#
private void OnAssistantOpening(object sender, InlineAIAssistantOpeningEventArgs e)
{
	e.Cancel = string.IsNullOrEmpty(e.SelectedText);
}
VB.NET
Private Sub OnAssistantOpening(sender As Object, e As InlineAIAssistantOpeningEventArgs)
	e.Cancel = String.IsNullOrEmpty(e.SelectedText)
End Sub

The popup ignores ordinary outside mouse clicks. It can close on Escape, a call to Close, an application focus change, or host changes. AutoCloseOnFocusLost controls application activation changes; AutoCloseOnHostChanged controls host-size and provider-reported viewport changes. Moving, resizing, or closing the containing form still requests a close. Outside mouse-wheel closing also depends on the popup manager's settings.

Canceling Closing prevents the close and leaves an active request running. Closing does not automatically clear the response; call ClearResponse in a Closed handler if each opening must start without the previous response.

Intercepting Commands

CommandExecuting is raised before a dropdown command submits its prompt. InlineAIAssistantCommandEventArgs exposes Command, a writable Prompt, and Cancel. Change the prompt or cancel submission in this event.

The selected command's Executed event signals submission, not completion of the AI response. See Configuring Commands for an example.

Intercepting Response Actions

ResponseActionExecuting is raised before Insert, Replace, or Discard. InlineAIAssistantResponseActionEventArgs exposes Action, writable ResponseText, and Cancel. Use it to validate or change the text before the provider applies it.

Registering the response-action handler

C#
this.assistant.ResponseActionExecuting += this.OnResponseActionExecuting;
VB.NET
AddHandler Me.assistant.ResponseActionExecuting, AddressOf Me.OnResponseActionExecuting

Rejecting empty edits while allowing Discard

C#
private void OnResponseActionExecuting(
	object sender, InlineAIAssistantResponseActionEventArgs e)
{
	if (e.Action != InlineAIAssistantResponseAction.Discard)
	{
		e.Cancel = string.IsNullOrWhiteSpace(e.ResponseText);
	}
}
VB.NET
Private Sub OnResponseActionExecuting(
	sender As Object, e As InlineAIAssistantResponseActionEventArgs)

	If e.Action <> InlineAIAssistantResponseAction.Discard Then
		e.Cancel = String.IsNullOrWhiteSpace(e.ResponseText)
	End If
End Sub

The provider's capability checks run after this event and use the potentially modified response. ResponseActionExecuted is raised after the action is applied. For Insert and Replace, it occurs before the subsequent close request. Setting Cancel after execution cannot undo an edit.

Command Types

Type	Description
`InlineAIAssistantCommand`	A selectable entry with `Text`, `Prompt`, `Icon`, and `Tag`. Its `Executed` event signals prompt submission, not completion of the AI response.
`InlineAIAssistantCommandGroup`	A group with `Text`, `Icon`, `Tag`, and a child `Commands` collection.

The command's Prompt is submitted when provided; otherwise, its display Text is used. Commands describe requests; the application implements the service call that performs them.

Custom Interaction Providers

Implement IInlineAIAssistantInteractionProvider for a host that does not have a built-in integration. Provide TargetControl, FullText, and SelectedText; implement TryGetAnchorRectangle in screen coordinates; and implement the capability checks and insertion and replacement methods.

Assign the provider to InteractionProvider before opening the assistant. To report scrolling or other viewport changes that invalidate the anchor, also implement IInlineAIAssistantViewportChangeNotifier. The assistant listens for ViewportChanged while open when deciding whether to close.

The assistant disposes providers it creates through AttachTo. Your application is responsible for disposing a custom provider it assigns, if that provider implements IDisposable.