如何摆脱错误“未设置为对象实例的对象引用”。 [英] How do I get rid of the error "object reference not set to an instance of an object."?
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问题描述
您好，我遇到此问题：
Object reference not set to an instance of an object.。
我尝试了以下代码，但它不起作用。它让我看到这个错误。
请帮忙。
问候
Aman Chaurasia
我尝试过：
.
I have tried the following code but it does not work. It keeps n showing me this error.
Please help.
Regards
Aman Chaurasia
What I have tried:
this.Cursor = Cursors.WaitCursor;
string UnpackDirectory = "";
string UnpackFile = "";
string SourceFolder = "";
UnpackDirectory = System.IO.Path.GetDirectoryName(StructureFileName);
UnpackFile = System.IO.Path.GetFileNameWithoutExtension(StructureFileName);
string EpubFolder = "";
EpubFolder = UnpackDirectory + "\\" + UnpackFile + "_Epub";
SourceFolder = EpubFolder + "\\OPS";
string StrBooKTitle = "";
StrBooKTitle = txt_BookTitle.Text;
if (Regex.IsMatch(StrBooKTitle, "\n" + "|" + "\r", RegexOptions.Multiline))
{
StrBooKTitle = Regex.Replace(StrBooKTitle, "\n" + "|" + "\r", "", RegexOptions.Multiline);
}
if (!string.IsNullOrEmpty(StrBooKTitle.Trim(' ')))
{
if (System.IO.Directory.Exists(SourceFolder))
{
System.IO.DirectoryInfo di = new System.IO.DirectoryInfo(SourceFolder);
System.IO.FileInfo[] dinfo = di.GetFiles("article_*.xml", SearchOption.TopDirectoryOnly);
if (dinfo.Length > 0)
{
Array.Sort(dinfo, new FileNameComparer());
string StrSectionHead = "";
string StrSectionFoot = "";
string StrSectionBody = "";
StrSectionHead = StrSectionHead + "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" + Environment.NewLine;
StrSectionHead = StrSectionHead + "<html xmlns:ncr=\"http://www.nytimes.com/NewsClientReader#\" xmlns=\"http://www.w3.org/1999/xhtml\" xmlns:nitf=\"http://www.nytimes.com/applicationdata/xml/nitf-3-3.dtd\">" + Environment.NewLine;
StrSectionHead = StrSectionHead + "<head>" + Environment.NewLine;
StrSectionHead = StrSectionHead + "<title>" + StrBooKTitle + "</title>" + Environment.NewLine;
StrSectionHead = StrSectionHead + "<link rel=\"stylesheet\" href=\"css/TablesAndFloats.css\" type=\"text/css\"></link>" + Environment.NewLine;
StrSectionHead = StrSectionHead + "</head>" + Environment.NewLine;
StrSectionHead = StrSectionHead + "<body>" + Environment.NewLine;
StrSectionHead = StrSectionHead + "<div class=\"clean\"/>" + Environment.NewLine;
StrSectionHead = StrSectionHead + "<div id=\"header\" class=\"masthead\">" + Environment.NewLine;
StrSectionHead = StrSectionHead + "<!--<img class=\"masthead-img\" src=\"images/###.jpg\" alt=\"Images\"/>-->" + Environment.NewLine;
StrSectionHead = StrSectionHead + "<div class=\"sectionName\">" + TitleTextBox.Text + "</div>" + Environment.NewLine;
string dDate = "";
string dMonth = "";
string dYear = "";
dDate = DateTime.Now.Day.ToString();
if (dDate.Length == 1)
{
dDate = "0" + dDate;
}
dMonth = DateTime.Now.Month.ToString();
if (dMonth.Length == 1)
{
dMonth = "0" + dMonth;
}
dYear = DateTime.Now.Year.ToString();
StrSectionHead = StrSectionHead + "<div id=\"header_date\" class=\"masthead-date\">" + dYear + "-" + dMonth + "-" + dDate + "</div>" + Environment.NewLine;
StrSectionHead = StrSectionHead + "</div>" + Environment.NewLine;
StrSectionFoot = StrSectionFoot + "<div class=\"article-spacer\"/>" + Environment.NewLine;
StrSectionFoot = StrSectionFoot + "</body>" + Environment.NewLine;
StrSectionFoot = StrSectionFoot + "</html>";
int ArticleBodyCount = 1;
string[] TempSectionStringArray = null;
string TempSectionString = "";
string[] TempSectionTitleArray = null;
string TempSectionTitleString = "";
int TSection = 0;
int TLastSection = 0;
string TArticle = "";
if (DataGridView1.RowCount > 0)
{
for (var irow = 0; irow < DataGridView1.RowCount; irow++)
{
if (DataGridView1.Rows[irow].Cells[0].Value != null)
{
if (Convert.ToString(DataGridView1.Rows[irow].Cells[2].Value) == "article-full-headline")
{
if (TLastSection != TSection)
{
TLastSection = TSection;
if (string.IsNullOrEmpty(TempSectionString))
{
TempSectionString = TempSectionString + TSection + "|" + "article_" + DataGridView1.Rows[irow].Cells[0].Value + "-" + DataGridView1.Rows[irow].Cells[1].Value;
}
else
{
TempSectionString = TempSectionString + Environment.NewLine + TSection + "|" + "article_" + DataGridView1.Rows[irow].Cells[0].Value + "-" + DataGridView1.Rows[irow].Cells[1].Value;
}
TArticle = "article_" + DataGridView1.Rows[irow].Cells[0].Value + "-" + DataGridView1.Rows[irow].Cells[1].Value;
}
else if (TArticle != "article_" + DataGridView1.Rows[irow].Cells[0].Value + "-" + DataGridView1.Rows[irow].Cells[1].Value)
{
if (string.IsNullOrEmpty(TempSectionString))
{
TempSectionString = TempSectionString + TSection + "|" + "article_" + DataGridView1.Rows[irow].Cells[0].Value + "-" + DataGridView1.Rows[irow].Cells[1].Value;
}
else
{
TempSectionString = TempSectionString + Environment.NewLine + TSection + "|" + "article_" + DataGridView1.Rows[irow].Cells[0].Value + "-" + DataGridView1.Rows[irow].Cells[1].Value;
}
TArticle = "article_" + DataGridView1.Rows[irow].Cells[0].Value + "-" + DataGridView1.Rows[irow].Cells[1].Value;
}
}
else if (Convert.ToString(DataGridView1.Rows[irow].Cells[2].Value) == "sectionName")
{
TSection = TSection + 1;
if (string.IsNullOrEmpty(TempSectionTitleString))
{
TempSectionTitleString = TempSectionTitleString + TSection + "|" + Convert.ToString(DataGridView1.Rows[irow].Cells[4].Value).Trim(' ');
}
else
{
TempSectionTitleString = TempSectionTitleString + Environment.NewLine + TSection + "|" + DataGridView1.Rows[irow].Cells[3].Value;
}
}
else
{
continue;
}
}
}
}
if (TSection == 0)
{
foreach (var ArticleFile in dinfo)
{
try
{
string tstrFileContent = "";
tstrFileContent = Common.ReadFile(ArticleFile.FullName);
StrSectionBody = StrSectionBody + "<div class=\"article-spacer\"/>" + Environment.NewLine;
StrSectionBody = StrSectionBody + "<div id=\"preview_" + ArticleBodyCount + "\" class=\"sectionArticleBlockOdd\">" + Environment.NewLine;
StrSectionBody = StrSectionBody + "<div class=\"sectionArticleTextBlock\">" + Environment.NewLine;
StrSectionBody = StrSectionBody + "<div class=\"sectionArticleTitle\">" + Environment.NewLine;
StrSectionBody = StrSectionBody + "<a class=\"sectionArticleLink\" href=\"" + ArticleFile.Name + "\">" + Environment.NewLine;
string ArticleHeadTitle = "";
if (Regex.IsMatch(tstrFileContent, "<h2 id=.+>(.+?)</h2>", RegexOptions.Multiline))
{
ArticleHeadTitle = Regex.Match(tstrFileContent, "<h2 id=.+>(.+?)</h2>", RegexOptions.Multiline).Groups[1].Value;
}
StrSectionBody = StrSectionBody + "<span id=\"preview_" + ArticleBodyCount + "_headline\" class=\"sectionArticleHeadline\">" + ArticleHeadTitle + "</span>" + Environment.NewLine;
StrSectionBody = StrSectionBody + "</a>" + Environment.NewLine;
StrSectionBody = StrSectionBody + "<div id=\"preview_" + ArticleBodyCount + "_byline\" class=\"sectionArticleByline\"/>" + Environment.NewLine;
string ArticleHeadBody = "";
if (Regex.IsMatch(tstrFileContent, "<p class=\"article-full-body\">(.+?)</p>", RegexOptions.Multiline))
{
ArticleHeadBody = Regex.Match(tstrFileContent, "<p class=\"article-full-body\">(.+?)</p>", RegexOptions.Multiline).Groups[1].Value;
if (ArticleHeadBody.Length > 50)
{
ArticleHeadBody = ArticleHeadBody.Substring(0, 50);
}
}
StrSectionBody = StrSectionBody + "<div id=\"preview_" + ArticleBodyCount + "_snippet\" class=\"sectionArticleBody\">" + ArticleHeadBody + "...</div>" + Environment.NewLine;
StrSectionBody = StrSectionBody + "</div>" + Environment.NewLine;
StrSectionBody = StrSectionBody + "</div>" + Environment.NewLine;
StrSectionBody = StrSectionBody + "</div>" + Environment.NewLine;
ArticleBodyCount = ArticleBodyCount + 1;
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString(), "Error Sections", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
StrSectionBody = StrSectionHead + StrSectionBody + StrSectionFoot;
Common.WriteFile(SourceFolder + "\\" + "section.xml", StrSectionBody);
btn_Sections.ForeColor = System.Drawing.Color.Red;
MessageBox.Show("Completed Sections", "ePUB Sections", MessageBoxButtons.OK, MessageBoxIcon.Information);
}
else
{
bool SectionsWritten = false;
for (var icm = 0; icm <= TempSectionTitleArray.Length; icm++)
{
if (!string.IsNullOrEmpty(TempSectionTitleArray[icm]))
{
int tSectionNo = Convert.ToInt32(Regex.Match(TempSectionTitleArray[icm], "(.+)\\|").Groups[1].Value);
string tSectionTitle = (Regex.Match(TempSectionTitleArray[icm], "\\|(.+)").Groups[1].Value).Trim(' ');
string TStrSectionHead = "";
TStrSectionHead = StrSectionHead;
TStrSectionHead = Regex.Replace(TStrSectionHead, "<div class=\"sectionName\">###</div>", "<div class=\"sectionName\">" + tSectionTitle + "</div>", RegexOptions.Multiline);
for (var ic = 0; ic < TempSectionStringArray.Length; ic++)
{
if (!string.IsNullOrEmpty(TempSectionStringArray[ic]))
{
string ArticleSectionTitleNo = Convert.ToInt32(Regex.Match(TempSectionStringArray[ic], "(.+)\\|").Groups[1].Value).ToString();
if (ArticleSectionTitleNo == tSectionNo.ToString())
{
string ArticleFileStr = Regex.Match(TempSectionStringArray[ic], "\\|(.+)").Groups[1].Value;
foreach (var ArticleFile in dinfo)
{
string tArtName = null;
tArtName = ArticleFile.Name;
if (tArtName.Contains(ArticleFileStr))
{
try
{
//===========================================
string tstrFileContent = "";
tstrFileContent = Common.ReadFile(ArticleFile.FullName);
StrSectionBody = StrSectionBody + "<div class=\"article-spacer\"/>" + Environment.NewLine;
StrSectionBody = StrSectionBody + "<div id=\"preview_" + ArticleBodyCount + "\" class=\"sectionArticleBlockOdd\">" + Environment.NewLine;
StrSectionBody = StrSectionBody + "<div class=\"sectionArticleTextBlock\">" + Environment.NewLine;
StrSectionBody = StrSectionBody + "<div class=\"sectionArticleTitle\">" + Environment.NewLine;
StrSectionBody = StrSectionBody + "<a class=\"sectionArticleLink\" href=\"" + ArticleFile.Name + "\">" + Environment.NewLine;
string ArticleHeadTitle = "";
if (Regex.IsMatch(tstrFileContent, "<h2 id=.+>(.+?)</h2>", RegexOptions.Multiline))
{
ArticleHeadTitle = Regex.Match(tstrFileContent, "<h2 id=.+>(.+?)</h2>", RegexOptions.Multiline).Groups[1].Value;
}
StrSectionBody = StrSectionBody + "<span id=\"preview_" + ArticleBodyCount + "_headline\" class=\"sectionArticleHeadline\">" + ArticleHeadTitle + "</span>" + Environment.NewLine;
StrSectionBody = StrSectionBody + "</a>" + Environment.NewLine;
StrSectionBody = StrSectionBody + "<div id=\"preview_" + ArticleBodyCount + "_byline\" class=\"sectionArticleByline\"/>" + Environment.NewLine;
string ArticleHeadBody = "";
if (Regex.IsMatch(tstrFileContent, "<p class=\"article-full-body\">(.+?)</p>", RegexOptions.Multiline))
{
ArticleHeadBody = Regex.Match(tstrFileContent, "<p class=\"article-full-body\">(.+?)</p>", RegexOptions.Multiline).Groups[1].Value;
if (ArticleHeadBody.Length > 50)
{
ArticleHeadBody = ArticleHeadBody.Substring(0, 50);
}
}
StrSectionBody = StrSectionBody + "<div id=\"preview_" + ArticleBodyCount + "_snippet\" class=\"sectionArticleBody\">" + ArticleHeadBody + "...</div>" + Environment.NewLine;
StrSectionBody = StrSectionBody + "</div>" + Environment.NewLine;
StrSectionBody = StrSectionBody + "</div>" + Environment.NewLine;
StrSectionBody = StrSectionBody + "</div>" + Environment.NewLine;
ArticleBodyCount = ArticleBodyCount + 1;
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString(), "Error Sections", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
}
}
else
{
break;
}
}
}
StrSectionBody = TStrSectionHead + StrSectionBody + StrSectionFoot;
Common.WriteFile(SourceFolder + "\\" + "section" + tSectionNo + ".xml", StrSectionBody);
StrSectionBody = "";
SectionsWritten = true;
}
}
if (SectionsWritten == true)
{
btn_Sections.ForeColor = System.Drawing.Color.Red;
MessageBox.Show("Completed Sections", "ePUB Sections", MessageBoxButtons.OK, MessageBoxIcon.Information);
}
else
{
MessageBox.Show("Sections not Complete", "Error Sections", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
}
else
{
MessageBox.Show("Articles Not Found, Generate and Try again", "Error Sections", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
else
{
MessageBox.Show("Structure Not Generated, Generate and Try Again", "Error Sections", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
else
{
MessageBox.Show("Book Title Blank", "Error Sections", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
this.Cursor = Cursors.Default;
btn_Toc.Enabled = true;
推荐答案
当您尝试使用null对象时可能会发生这种情况，就好像它是正确引用的对象。大多数情况下，当你尝试将值赋值给对象时，如果值为null，则会发生这种异常。
尝试将断点放在上面代码并找到具有空值的对象。
你可以检查这个类似的问题
c＃对象引用未设置为对象错误的实例
it can happen when you are trying to use a null object as if it was a properly referenced object. Most of the time, when you try to assing value into object, and if the value is null, then this kind of exception occur.
try to put break points on the code and find the object with null value.
you can check this similar question
c# Object reference not set to an instance of an object error
这是我们遇到的最常见问题之一，也是我们最不能回答的问题，但你最有能力回答自己。
让我解释一下错误的含义：你曾尝试使用变量，属性或方法返回值，但它包含null - 这意味着没有a的实例变量中的类。
这有点像一个口袋：你的衬衫里有一个口袋，用来握笔。如果你进入口袋并发现那里没有笔，你就不能在一张纸上签名 - 如果你尝试的话，你会得到非常有趣的外观！空口袋给你一个空值（这里没有笔！）所以你不能做任何你检索笔通常做的事情。它为什么空？这就是问题 - 可能是你今天早上离开家时忘了拿起你的笔，或者你昨晚把它拿到昨天的衬衫口袋里时可能会把笔留下来。
我们无法分辨，因为我们不在那里，更重要的是，我们甚至看不到你的衬衫，更不用说口袋里的东西了！
回到计算机，你做了同样的事情，不知何故 - 我们看不到你的代码，更不用说运行它了，找不到包含null的东西。
但是你可以 - 而Visual Studio将在这里帮助你。在调试器中运行您的程序，当它失败时，VS将向您显示它发现问题的行。然后，您可以开始查看它的各个部分，以查看哪个值为null，并开始回顾代码以找出原因。因此，在包含错误行的方法的开头放置一个断点，然后从头再次运行程序。这一次，VS会在错误发生前停止，让你通过查看代码来查看你的价值来检查发生了什么。
但我们做不到那 - 我们没有您的代码，如果我们拥有它，我们不知道如何使用它，我们没有您的数据。所以试试吧 - 看看你能找到多少信息！
This is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself.
Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.
It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterdays shirt when you took it off last night.
We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket!
Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't.
But you can - and Visual Studio will help you here. Run your program in the debugger and when it fails, VS will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, VS will stop before the error, and let you examine what is going on by stepping through the code looking at your values.
But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out!
这篇关于如何摆脱错误“未设置为对象实例的对象引用”。的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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