I am trying to programatically click the "save" button and test that the windows Save Dialog box appears: I have everything but the assert statement I believe. I don't know how to assert that my custom SaveDialogBox appears to the user.

[test]
public void Method_WhenThePersonIsNotfound_ClickingTheButtonSavesLetterToWordDocument
{
     //arrange
     CreateNewPage(); //creates IE window enters fields and clicks submit on first page.
     //act
     this.InternetExplorerDriver.FindElementById("SaveForm").Click();

     //assert
     //Assert statement to verify that when button was clicked the save dialog box to save the letter in word appears.