How do I get rid of the error "object reference not set to an instance of an object."?

Question

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VS2017

Hello, I am facing this issue:

Object reference not set to an instance of an object.

.

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;

Posted 23-May-18 22:38pm

Primo Chalice

Updated 23-May-18 23:01pm

v2

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Jinto Jacob · Answer 1 · 2018-05-23T23:00:00

Solution 1

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

Posted 23-May-18 23:00pm

Jinto Jacob

Updated 23-May-18 23:01pm

v2

Comments

Primo Chalice 24-May-18 6:36am

Dim TempSectionTitleArray As String() in Visual Basic
string[] TempSectionTitleArray = null; in C#

The Visual Basic code is working fine with no errors but it is showing an error in C#.

I used "string[] TempSectionTitleArray = new string[0];" but then the error is "Index was outside the bounds of the array."

Jinto Jacob 24-May-18 7:22am

you are trying to access an index in array which is not available.

for example if you try to access 4th element in an array of size 2 it will happen.

Primo Chalice 24-May-18 7:27am

But then how did it work in Visual Basic?

Jinto Jacob 24-May-18 8:08am

the equivalent of
Dim TempSectionTitleArray As String() is

string[] TempSectionTitleArray;

try it instead of string[] TempSectionTitleArray = new string[0]

Primo Chalice 24-May-18 8:47am

I actually tried that. I have a line after that

for (var icm = 0; icm < TempSectionTitleArray.Length; icm++)

Here, it says "Use of unassigned local variable"

OriginalGriff · Answer 2 · 2018-05-23T23:02:00

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!