Selenium webdriver window handles c# switchTo failed

Question

Here comes 2 windows pop out during the testing.

my code:

string BaseWindow = driver.CurrentWindowHandle;                 
ReadOnlyCollection

        

Answer 1

//switch to new window 
driver.FindElement(By.Id("link")).Click(); 

//wait for new window to open 
Thread.Sleep(2000); 

//get the current window handles 
string popupHandle = string.Empty; 
ReadOnlyCollection windowHandles = driver.WindowHandles;  

foreach (string handle in windowHandles)  
{  
    if (handle != existingWindowHandle)  
    {  
         popupHandle = handle; break;  
    }  
}  

 //switch to new window 
driver.SwitchTo().Window(popupHandle); 

//check for element on new page 
webElement = driver.FindElement(By.Id("four04msg")); 
if(webElement.Text == "THE CONTENT YOU REQUESTED COULDN’T BE FOUND...")  
{  
    return false;  
}  
else  
{  
    return true;  
}  

 //close the new window to navigate to the previous one
driver.close(); 

//switch back to original window 
driver.SwitchTo().Window(existingWindowHandle);