Hashtable error: "Object reference not set to an instance of ans object."

Okay, my project is almost finished and this seems to be the last bug. My error is on line 613 during the last 'while' code.  It seems that garbage collection has 'dumped' my initial 'hash' instance???   I then get the error message "Object reference not set to an instance of ans object."!

Q. How do I fix the code to eliminate the error???

try
{
while((line = reader.ReadLine()) != null)                        
{                  
string [] tmp = line.Split('\t');
if(tmp.Length == 2)
{
if(!hash.Contains(tmp[0]))
{
hash.Add(tmp[0], tmp[1]);
}                              
listBox1.Items.Add(tmp[0] + "\t" + tmp[1]);
}
}
}
finally
{
reader.Close();
}



while(myReader2.Read())
{
if (! hash.ContainsKey(str_col_DestIP.Trim()))
{
string strDestDns = "Use Other...";
}
else
{      
string str = (hash[1].ToString());     // line 613
}







LVL 1
kvnsdrAsked:
Who is Participating?
 
gregoryyoungCommented:
string str =  hash[str_col_DestIP.Trim()];

0
 
jjacksnCommented:
you can't just get out the first index, since you do'nt know that it exists....

the hash set could very well contain no keys or values, so hash[1] is not set to an object and that is why you are getting the error.  do what gergory said and index it by what you just found to be true.  
0
 
kvnsdrAuthor Commented:
I really appreciate all your patience. I hope I can code as well as you guys so I can return the favor... thank you very much!!!

Before I start my next question I would like to commet on the first part that you've already answered. I thought about using the "string str =  hash[str_col_DestIP.Trim()];", however some how I kept thinking about the hash[1] as the data. Well anyway it does make sense now that jjackson explained it too. Thanks again.....

I generally write very small programs and simply link all my code in one large mass. However, I'm trying to 'professionalize' my code. So, my next question concerns sharing the data in this method with other methods........

Q. How can I write this method correctly to 'pass' the hash data to another method???

private void LoadHashtable(object obj_hash)          // this first line is the problem.........
{
try
{
while((line = reader.ReadLine()) != null)                    
{              
string [] tmp = line.Split('\t');
if(tmp.Length == 2)
{
if(!hash.Contains(tmp[0]))
{
hash.Add(tmp[0], tmp[1]);
}                        
listBox1.Items.Add(tmp[0] + "\t" + tmp[1]);
}
}
}
finally
{
reader.Close();
}
0
Cloud Class® Course: Microsoft Office 2010

This course will introduce you to the interfaces and features of Microsoft Office 2010 Word, Excel, PowerPoint, Outlook, and Access. You will learn about the features that are shared between all products in the Office suite, as well as the new features that are product specific.

 
jjacksnCommented:
kvnsdr, this should go in another question perhaps.  

But, I don't really understand what you are asking...

If you want to get what is stuck into the hash table back after the end of the method, change it to:

private string LoadHashtable(object obj_hash)          // this first line is the problem.........
{
string [] tmp = null;
try
{
while((line = reader.ReadLine()) != null)                    
{              
tmp = line.Split('\t');
if(tmp.Length == 2)
{
if(!hash.Contains(tmp[0]))
{
hash.Add(tmp[0], tmp[1]);
}                        
listBox1.Items.Add(tmp[0] + "\t" + tmp[1]);
}
}
}
finally
{
reader.Close();
}
return tmp[1];
}

I'm not sure why you are using try/finally without a catch here, either.  

If this is not what you meant, please rephrase.

0
 
gregoryyoungCommented:
the try catch finally is because there is file io jjacksn the finally is closing the file.
0
 
jjacksnCommented:
I was wondering why there is no "Catch", the finally makes sense.  
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

All Courses

From novice to tech pro — start learning today.