循环检查重复产品标题：现有代码逻辑异常求助

Let's break down exactly why your current code isn't working as you expected, then walk through two solid fixes:

The Core Problem with Your Current Code #

Your main issue is re-fetching the productTitles element collection inside the outer loop. Here's what happens:

• When you first get productTitles, you have a collection of element references. You pick one as x.
• Then you re-run FindElements, which creates a brand new set of element references (even if they're the same UI elements, they're different objects in code).
• When you call productTitles.IndexOf(x), the new collection doesn't contain the old x reference, so it returns -1. That makes Skip(-1 + 1) = Skip(0), which completely breaks your intended "compare each element to all elements after it" logic.
• On top of that, re-fetching elements repeatedly is inefficient and risks stale element errors if the page updates mid-check.

Fix 1: Pre-Fetch All Titles to a String List #

The easiest fix is to pull all the title texts into a simple list first, then work with that list for your duplicate check. This avoids element reference confusion and redundant Selenium calls:

// Grab all product title texts in one single fetch
var productTitles = SeleniumContext.Driver.FindElements(By.XPath(ComparisonTableElements.ProductTitle))
    .Select(element => element.Text)
    .ToList();

// Check each title against all titles that come after it
for (int i = 0; i < productTitles.Count; i++)
{
    var currentTitle = productTitles[i];
    for (int j = i + 1; j < productTitles.Count; j++)
    {
        if (currentTitle == productTitles[j])
        {
            Assert.Fail("Found duplicate product in the table");
        }
    }
}

Fix 2: Use a HashSet for Faster Duplicate Detection #

If you don't need to know exactly which pairs are duplicates and just want to confirm there are none, a HashSet is a more efficient option (it runs in O(n) time instead of O(n²) like nested loops):

var seenTitles = new HashSet<string>();
var productElements = SeleniumContext.Driver.FindElements(By.XPath(ComparisonTableElements.ProductTitle));

foreach (var element in productElements)
{
    var title = element.Text;
    // HashSet.Add() returns false if the value is already in the set
    if (!seenTitles.Add(title))
    {
        Assert.Fail("Found duplicate product in the table");
    }
}

Why These Fixes Work #

• Both approaches only fetch the UI elements once, so you're working with a consistent set of values throughout the check.
• The string list approach keeps your original pairwise comparison logic intact but removes the element reference issues.
• The HashSet approach is cleaner and faster, as it automatically tracks which titles you've already seen.

内容的提问来源于stack exchange，提问作者Brian Mitchell