删除 c# 中字符串列表中的一个元素，给出错误（ArgumentOutOfRangeException）

Question

I'm trying to filter my string list by getting input, but get this error: ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index

private List<string> title = new List<string>();
private int cellNumber { get; set; }
private int counter = 0;

inputField.onValueChanged.AddListener(delegate { Search(cellNumber-counter); });

public void Search(int size)
{
    for (int i = 0; i < size; i++)
    {

        if (!title[i].ToLower().Contains(inputField.text.ToLower()) && inputField.text != "")
        {
            title.RemoveAt(i);
            counter++;
        }

    }
}

Answer 1

If you have hits your list size decreases for each removed item.

So even assuming you are passing in the correct size of the list, the iterator variable i at some point at the end runs longer than the new smaller size of your list after removing items => ArgumentOutOfRangeException!

---

What you could do is keep updating the size and skip i++ whenever you remove an item like eg

public void Search()
{
    if (string.IsNullOrWhiteSpace(inputField.text))
    {
        return;
    }

    var size = title.Count;
    var i = 0;

    while(i < size)
    {
        if (!title[i].ToLower().Contains(inputField.text.ToLower()))
        {
            title.RemoveAt(i);
            size--;
        }
        else
        {
            i++;
        }
    }
}

---

Note that there is a simple method that already covers this without further effort: List<t>.RemoveAll

public void Search()
{
    if(string.IsNullOrWhiteSpace(inputField.text))
    {
        return;
    }

    // remove all matches
    title.RemoveAll(t => !t.ToLower().Contains(inputField.text.ToLower()));
}

---

Though you might be even more interested in using Linq Where in order to return a new collection with the hits without modifying the original one

using System.Linq;

...

public string[] Search()
{
    if(string.IsNullOrWhiteSpace(inputField.text))
    {
        return new string[0];
    }

    // remove all matches
    return title.Where(t => t.ToLower().Contains(inputField.text.ToLower())).ToArray();
}