对象引用没有设置为对象的实例

private void btnmap_Click(object sender, EventArgs e)
{
    XmlDocument xmldoc = new XmlDocument();
    XmlNode xmlnode, xmlroot, docNode, Doc;
    XmlAttribute xmlatt;                                                  
    if (rchtextfile.Text == "")
    {
        MessageBox.Show("Please Select a Text file", "File Name Error", MessageBoxButtons.OK, MessageBoxIcon.Warning);
    }
    else
    {
        con = new System.Data.SqlClient.SqlConnection();
        DataSet ds = new DataSet();
        con.ConnectionString = @"Server=sql1; User ID=blah; Pwd=fubar; Initial Catalog=xml;";
        con.Open(); 
        MessageBox.Show("Database Connected");
        String sql = "select Styles from Xml_Tags,pdfelement where Xml_Tags.Mapping_Id=pdfelement.Mapping_Id AND Xml_Tags.Pdf_Tag=pdfelement.Element_Name AND pdfelement.Style=Xml_Tags.Styles";               
        com = new SqlCommand(sql);
        da = new System.Data.SqlClient.SqlDataAdapter(sql, con);
        da.Fill(ds, "xml");
        maxrows = ds.Tables["xml"].Rows.Count;
        StreamReader objReader = new StreamReader(file, Encoding.Default, true);                                                     
        do
        {                    
            for (int i = 0; i < maxrows; i++)
            {                            
                docNode = xmldoc.CreateXmlDeclaration("1.0", "UTF-8", null);
                //xmldoc.AppendChild(docNode);
                dRow = ds.Tables["xml"].Rows[i];                           
                line = objReader.ReadLine();
                string st1 = ">";
                string st2 = "</";
                int end = line.IndexOf(st2);
                if (end != -1 && end > 1)
                {
                    st = line.IndexOf(st1);
                    en = line.IndexOf(st2);
                    int v = en - st;
                    sub = line.Substring(st + 1, v - 1);
                    rchtext.Text = rchtext.Text + sub + "\r\n";
                }                              

                String sqll = "select Dtd_Tag from Xml_Tags,pdfelement where Xml_Tags.Mapping_Id=pdfelement.Mapping_Id AND Xml_Tags.Pdf_Tag=pdfelement.Element_Name AND pdfelement.Style=Xml_Tags.Styles";
                SqlCommand comm = new SqlCommand(sqll);
                SqlDataAdapter daa = new System.Data.SqlClient.SqlDataAdapter(sqll, con);
                DataSet ds1 = new DataSet();
                daa.Fill(ds1, "xml");
                dRow1 = ds1.Tables["xml"].Rows[i];
                //String sqlll = "select Dtd_Attribute_Name from Mapped_Tags_Attributes,Xml_Tags where Mapped_Tags_Attributes.Pdf_Tag=Xml_Tags.Pdf_Tag";
                String sqlll = "select Dtd_Attribute_Name from Mapped_Tags_Attributes,Xml_Tags where Mapped_Tags_Attributes.Pdf_Tag=Xml_Tags.Pdf_Tag AND Mapped_Tags_Attributes.Mapping_Id=Xml_Tags.Mapping_Id";
                SqlCommand cmd = new SqlCommand(sqlll);
                SqlDataAdapter dt = new System.Data.SqlClient.SqlDataAdapter(sqlll, con);
                DataSet ds2 = new DataSet();
                dt.Fill(ds2, "xml");
                dRow2 = ds2.Tables["xml"].Rows[i];
                name = XmlConvert.EncodeName(dRow1.ItemArray.GetValue(0).ToString());
                xmlnode = xmldoc.CreateElement(name);
                Doc = xmldoc.CreateDocumentType(name, null, "E:\\Rachana_mds\\proj\\pdfextraction\\docbook.dtd", null);
                //xmldoc.AppendChild(Doc); 
                xmlroot = xmldoc.CreateElement(name);
                //xmldoc.AppendChild(xmlroot);
                xmlatt = xmldoc.CreateAttribute(dRow2.ItemArray.GetValue(0).ToString());
                xmlroot.AppendChild(xmlnode);
                xmlnode.InnerText = sub;                                
            }
        }
        while (dRow[0].ToString() != line && objReader.Peek() != -1);

        MessageBox.Show("Done XML")                            
        saveFileDialog1.Filter = "XML Files (*.xml)|*.xml";
        if (saveFileDialog1.ShowDialog() == DialogResult.OK)
        {
            StreamWriter ya=new StreamWriter (saveFileDialog1.FileName.ToString());   
            xmldoc.Save(ya);
        }
        else
        {
            return;
        }
    }
    MessageBox.Show("Successfully saved");                                    
    con.Close();               
    }       
}

I am getting error at the int end = line.IndexOf(st2); line

在int端= line.IndexOf(st2)行

4 个解决方案

#1

If you're getting a NullReferenceException on

如果您正在获取NullReferenceException

int end = line.IndexOf(st2);

then line must be null. You should find out why - my guess is that there aren't as many lines in the file as you expect. (TextReader.ReadLine returns null when it's run out of data.)

那么行必须为空。您应该找出原因——我的猜测是，文件中没有您期望的那么多行。(TextReader。ReadLine在耗尽数据时返回null。

Additionally:

另外:

This method is large, and hard to read. Try to refactor it into smaller chunks.
这个方法很大，很难阅读。试着把它重构成更小的块。
Use using statements for resources such as StreamReader and SqlConnection
对资源(如StreamReader和SqlConnection)使用using语句
Using LINQ to XML would probably make the XML part simpler
使用LINQ to XML可能会使XML部分更简单。
Rather than using objReader.Peek, check for the line being null to detect the end of input
而不是使用objReader。Peek，检查行是否为空，以检测输入的结束
(Relatively advanced) If this is in a client app, doing all of this work in the UI thread is going to lock up the UI. You should perform long-running tasks in a different thread.
(相对高级)如果这是在客户端应用程序中，在UI线程中做所有这些工作将会锁定UI。您应该在不同的线程中执行长时间运行的任务。

#2

probably objReader.ReadLine(); returns null, so

可能objReader.ReadLine();返回null,所以

line = objReader.ReadLine();

doesn't work as supposed

不应该工作

#3

check that line is null or not:

检查该行是否为空:

int end;
if(line != null)
   end= line.IndexOf(st2);

#4

-1

Firstly, Try to format a bit better the code is unreadeable.

首先，试着把代码格式化得更好一点，因为代码是不可读的。

The problem is that any of the object is not initialized.

问题是任何对象都没有初始化。

#1