Xml reading through c# null reference exception

Question

My code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml;
using System.Xml.Linq;
using System.Globalization;
namespace Read_Attribute
{
    class Program
    {
        static void Main(string[] args)
        {
            String path = @"C:\\Users\\Sunny\\Documents\\Visual Studio 2012\\Projects\\taskl\\taskl\\bin\\Debug\\procy.xml";
            XmlDocument xml = new XmlDocument();
            using (XmlTextReader tr = new XmlTextReader(path))
            {
                tr.Namespaces = false;
                xml.Load(tr);
            }
            XmlNodeList list = xml.GetElementsByTagName("omgdc:Bounds");
            XmlNodeList listt = xml.GetElementsByTagName("task");
            bool flag = true;
            bool flag1 = true;

            Double x1 = 0, x2 = 0, y1 = 0, y2 = 0;

            string c1 = null;
            string c2 = null;
            string v1 = null;
            string v2 = null;

            foreach (XmlNode m in listt)
            {
                if (m.Attributes.Count > 0)
                {
                    if (flag1)
                    {
                        c1 = (m.Attributes["id"].InnerText);
                        v1 = (m.Attributes["id"].InnerText);
                        flag1 = false;
                        Console.WriteLine("The id of task is :" + c1, "The id of task is :" + v1);
                    }
                    else
                    {
                        c2 = (m.Attributes["id"].InnerText);
                        v2 = (m.Attributes["id"].InnerText);
                        flag1 = true;

                        Console.WriteLine("The id of task is :" + c2, "The id of task is :" + v2);
                    }
                }
            }

            foreach (XmlNode n in list)
            {
                String idStr = n.Attributes["id"].InnerText;    
            if ((idStr != null) && ((idStr == c1) || (idStr == v1) || (idStr == c2) || (idStr == v2)))

                    {
                        if (flag)
                        {
                            x1 = Convert.ToDouble(n.Attributes["x"].InnerText);
                            y1 = Convert.ToDouble(n.Attributes["y"].InnerText);
                            flag = false;
                            Console.WriteLine("The dimension of x is :" + x1);
                            Console.WriteLine("The dimension of y is :" + y1);

                        }
                        else
                        {
                            x2 = Convert.ToDouble(n.Attributes["x"].InnerText);
                            y2 = Convert.ToDouble(n.Attributes["y"].InnerText);
                            flag = true;

                            if (x2 > x1)
                            {
                                Console.WriteLine("The tasks don't overlap with each other");

                            }
                            else
                                Console.WriteLine("The tasks overlap with each other");
                        }
                    }
                }
            }
        }
    }

String idStr = n.Attributes["id"].InnerText there was a null reference exception at this point how to remove this error i want to read XML through this code of a business process model kindly help me in removing the error as soon as possible Thankx in advance for ur help

Answer 1

Its difficult to identify exact error without knowing what XML looks like. But there are few correction which may work for null reference.

1) Is the path correct?

String path = @"C:\\Users\\Sunny\\Documents\\Visual Studio 2012\\Projects\\taskl\\taskl\\bin\\Debug\\procy.xml";

Any particular reason for extra escape character even when using @ ? I believe it should be like

String path = @"C:\Users\Sunny\Documents\Visual Studio 2012\Projects\taskl\taskl\bin\Debug\procy.xml";

Which means first check is, whether xml is actually getting loaded?

2) Add a check for Attributes :

Something like

if (n.Attributes["id"] != null)

3) Sure you need InnerText or is it value instead?

Perhaps try this

String attributeValue = n.Attributes["id"].Value;