Selenium webdriver 窗口处理 c# switchTo 失败

测试过程中会弹出 2 个窗口。

my code:

string BaseWindow = driver.CurrentWindowHandle;                 
ReadOnlyCollection<string> handles = driver.WindowHandles;

foreach(string handle in handles)                    
{                         
    Boolean a = driver.SwitchTo().Window(handle).Url.Contains("Main");
    if (a == true)  
    {       
        InitialSetting.driver.SwitchTo().Window(handle);      
        break;
    }  
}                

我想切换到 url 包含“Main”的窗口。但测试运行时，它不断地在两个窗口之间切换，并且不停歇。

我调试并发现foreach没有收支平衡时boolean a是真的。

我该如何解决这个问题？

//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<string> 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);