索引超出范围.必须是非负数，小于集合大小

Question

>我有两个字符串列表(girlsLIST1 和 girlsLIST2(，其中我有 5 个字符串值，但是当我将这些值增加到 6 时，我得到一个例外这是我的代码。 现在，我根据问题变量的值(for循环运行(具有问题变量，并从列表中选择一些随机字符串，并将这些结果存储在girl1names和girl2names列表中。目前我的问题变量的值是 5，但如果我将我的 girlsLIST1 和 girlsLIST2 列表中的字符串增加到 5 以上，那么我就会得到一个异常。

List<string> girlsLIST1 = new List<string> { "Aliya", "Manal", "Ayman", "Laiba", "Lubna", "Aziza" };
List<string> girlsLIST2 = new List<string> { "Mehmoona", "Samra", "Saria", "Aleena", "Faiza","Mehwish" };
List<string> girl1names = new List<string>();
List<string> girl2names = new List<string>();
int GirlName;
int GirlName2;
if (addquestions == true)
{
    //for (int i = 0; i <girlsLIST1.Count; i++)
    //{
    //    int Girlsnames1 = random.Next(girlsLIST1.Count);
    //    GirlName = girlsLIST1[Girlsnames1];
    //}
    //for (int i = 0; i < girlsLIST2.Count; i++)
    //{
    //    int Girlsnames2 = random.Next(girlsLIST2.Count);
    //    GirlName2 = girlsLIST2[Girlsnames2];
    //}
    var random = new Random();
    int min = 2;
    int max = 10;
    for (int i = 0; i < questions; i++)
    {
        GirlName = random.Next(girlsLIST1.Count);
        GirlName2 = random.Next(girlsLIST2.Count);
        girl1names.Add(girlsLIST1[GirlName]);
        girl2names.Add(girlsLIST2[GirlName2]);
    }
    var list = new List<string>
    {
        girl1names[GirlName] +" was playing basketball. " + random.Next(min, max) + " of her shots went in the hoop. " + random.Next(min, max) + " of her shots did not go in the hoop. How many shots were there in total?",
        "The restaurant has " + random.Next(min, max) + " normal chairs and " + random.Next(min, max) +" chairs for babies. How many chairs does the restaurant have in total?",
        "How many cookies did you sell if you sold " + random.Next(min, max) + " chocolate cookies and " + random.Next(min, max) + " vanilla cookies?",
        girl2names[GirlName2] + " bought a big bag of candy. The bag had " + random.Next(min, max) + " blue candies, " + random.Next(min, max) + " red candies and " + random.Next(min, max) + " green candies. How many candies were there in total?",
        girl1names[GirlName] + " had " + random.Next(min, max) + " books at home. He went to the library to take out " + random.Next(min, max) + " more books. He then bought 1 book. How many books does Billy have now?",
        "The hobby store normally sells " + random.Next(min, max) + " trading cards per month. In June, the hobby store sold " + random.Next(min, max) + " more trading cards than normal. In total, how many trading cards did the hobby store sell in June?",
        girl2names[GirlName2] + " has " + random.Next(min, max) + " pieces of gum to share with her friends. There wasn’t enough gum for all her friends, so she went to the store to get " + random.Next(min, max) + " more pieces of gum. How many pieces of gum does Adrianna have now?",
        girl1names[GirlName] + " has " + random.Next(min, max) + " pieces of gum to share with her friends. There wasn’t enough gum for all her friends, so she went to the store and got " + random.Next(min, max) + " pieces of strawberry gum and " + random.Next(min, max) + " pieces of bubble gum. How many pieces of gum does Adrianna have now?"
    };
    genericfunction(list);
    //int index = randoms.Next(list.Count);
    //DisplayAlert("word problems", list[index], "ok");
    //Creates a new Word document 
    WordDocument wordDocument = new WordDocument();
    //Adds new section with single paragraph to the document
    wordDocument.EnsureMinimal();
    wordDocument.LastSection.PageSetup.Margins.All = 15;
    //Get Last paragraph of the document
    IWParagraph paragraph = wordDocument.LastParagraph;
    //Create a custom style
    WParagraphStyle paragraphStyle = wordDocument.Styles.FindByName("Normal") as WParagraphStyle;
    paragraphStyle.CharacterFormat.Font = new Syncfusion.Drawing.Font("Times New Roman", 20);
    paragraphStyle.ParagraphFormat.HorizontalAlignment = HorizontalAlignment.Justify;
    paragraphStyle.ParagraphFormat.AfterSpacing = 15f;
    WSection section = wordDocument.LastSection;
    for (int i = 0; i < wordproblemslist.Count; i++)
    {
        paragraph = section.AddParagraph();
        string t = wordproblemslist[i];
        paragraph.AppendText(t);
    }
    //Adds new text to the paragraph
    //paragraph.AppendText(text);
    //Adds first text to the paragraph
    //  paragraph = section.AddParagraph();
    // paragraph.AppendText(text);
    //Second paragraph
    //  paragraph = section.AddParagraph();
    //  paragraph.AppendText(text);
    //Instantiation of DocIORenderer for Word to PDF conversion
    DocIORenderer render = new DocIORenderer();
    //Converts Word document into PDF document
    PdfDocument pdfDocument = render.ConvertToPDF(wordDocument);
    //Releases all resources used by the Word document and DocIO Renderer objects
    render.Dispose();
    wordDocument.Dispose();
    //Save the document into memory stream
    MemoryStream stream = new MemoryStream();
    pdfDocument.Save(stream);
    stream.Position = 0;
    //Close the document 
    pdfDocument.Close();
    //Save the stream into pdf file
    //The operation in Save under Xamarin varies between Windows Phone, Android and iOS platforms. Please refer PDF/Xamarin section for respective code samples.
    Xamarin.Forms.DependencyService.Get<ISave>().SaveAndView("Output.pdf", "application/pdf", stream);
    wordproblemslist.Clear();
    girl1names.Clear();
    girl2names.Clear();
    private void genericfunction( List<string> list)
    {
        var random = new Random();
        List<int> listNumbers = new List<int>();
        int number;
        for (int j = 0; j < questions; j++)
        {
            do
            {
                number = randoms.Next(list.Count);
            } while (listNumbers.Contains(number));
            listNumbers.Add(number);
        }
        for (int k = 0; k < listNumbers.Count; k++)
        {
            wordproblemslist.Add(list[listNumbers[k]]);
        }
    }

Answer 1

您以这种方式初始化GirlName：

GirlName = random.Next(girlsLIST1.Count);

所以在这里，GirlName将介于0和5之间。

然后，您尝试以这种方式从girl1names中获取名称：

girl1names[GirlName]

但是，girl1names只包含questions名称，因为您以这种方式填写了此列表：

for (int i = 0; i < questions; i++)
{
    girl1names.Add(girlsLIST1[GirlName]);
}

因此，如果碰巧GirlName大于或等于questions，你就出局了。

(girl2names[GirlName2]也是如此(

---

溶液

不要尝试访问girl1names[GirlName] 。

使用不会超过girl1names长度的索引(也许重新考虑您真正想要达到的索引，因为GirlName不太可能是您要查找的索引(

girl2names也一样。

Answer 2

原因：

您得到的异常表明Index Was Out Of Range. Must Be Non Negative And Less Then The Size Of Collection意味着您要获取的对象索引超出了范围。

它发生在这里：girl1names[GirlName]和girl2names[GirlName2].

girl1names ：这是一个保存名称的列表。其计数取决于问题value。

GirlName：在这里按Index工作。它的最大值取决于girlsLIST1.Count。

为了防止出现异常，应确保 GirlName 的值小于 girl1names 的长度。

所以，这意味着，你定义的girlsLIST1.Count的值应该小于问题。(同girl2names[GirlName2](

我猜你的问题值小于 4，所以如果你将 5 个字符串值增加到 6，它会崩溃。

溶液：

确保问题的价值大于 girlsLIST1.Count 和 girlsLIST2.Count。