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public override async Task OnTurnAsync(ITurnContext turnContext, CancellationToken cancellationToken = default)
{
    await base.OnTurnAsync(turnContext, cancellationToken);

    // Save any state changes that might have occurred during the turn.
    await ConversationState.SaveChangesAsync(turnContext, false, cancellationToken);
    await UserState.SaveChangesAsync(turnContext, false, cancellationToken);
var text = turnContext.Activity.Text;
        if (text == "hello")
        {
            await Dialog.RunAsync(turnContext, ConversationState.CreateProperty<DialogState>(nameof(DialogState)), cancellationToken);
        }
        else 
        {
            await turnContext.SendActivityAsync("waiting for dailog");
        }
        await base.OnTurnAsync(turnContext, cancellationToken);

}

protected override async Task OnMessageActivityAsync(ITurnContext<IMessageActivity> turnContext, CancellationToken cancellationToken)
{
    Logger.LogInformation("Running dialog with Message Activity.");

    // Run the Dialog with the new message Activity.
    await Dialog.RunAsync(turnContext, ConversationState.CreateProperty<DialogState>(nameof(DialogState)), cancellationToken);
}