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Error is In this Line
con.Open();
Error is :- Cannot open Connection:System.NullReferenceException:Object Reference Not
set to an instance of an object.
 
its not problem in other form its only prroblem in this code...
 
           try
           {
               con.Open();
               str = "select *from DatabaseLogin where user_id='" + textBox2.Text + "'";
               com = new OleDbCommand(str, con);
               OleDbDataReader reader = com.ExecuteReader();
               while (reader.Read())
               {
                   checkedListBox1.Items.Add(reader["stckdemge"]);
               }
           }
           catch (Exception ex)
           {
               MessageBox.Show(" " + ex);
           }
Posted 28-Feb-13 2:02am
Edited 28-Feb-13 2:10am
v2
Comments
S.P. Tiwari at 28-Feb-13 7:08am
   
where u created connection object? and assign the connection string. give more details..
kashifjaat at 28-Feb-13 21:38pm
   
OleDbConnection cn;
public ExpireProduct()
{
InitializeComponent();

cn = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=D:\MIS SYSTEM\AniPharmic\AniPharmic\MedicalDb.accdb;Jet OLEDB:Database Password=");

}
 
this connection string I use ....But my problem not solve
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Solution 1

The error message is pretty clear:
Object Reference Not set to an instance of an object.
Since it occurs on a line as simple as this:
con.Open();
it can only be one thing: the variable con has been declared, but you have not assigned a value to it - hence, it is null
 
At some point before this code, you need to execute something like:
con = new OleDbConnection(strConnect);
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Comments
nv3 at 28-Feb-13 7:16am
   
As simple as that :-) 5.
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Solution 3

you had made "cn" as connection object
and you use "con", how would it works.
 
You should write..
 
OleDbConnection con;
public ExpireProduct() { InitializeComponent();
con= new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=D:\MIS SYSTEM\AniPharmic\AniPharmic\MedicalDb.accdb;Jet OLEDB:Database Password="); }
 
try
           {
               con.Open();
               str = "select *from DatabaseLogin where user_id='" + textBox2.Text + "'";
               com = new OleDbCommand(str, con);
               OleDbDataReader reader = com.ExecuteReader();
               while (reader.Read())
               {
                   checkedListBox1.Items.Add(reader["stckdemge"]);
               }
con.Close();
           }
           catch (Exception ex)
           {
               MessageBox.Show(" " + ex);
           }
  Permalink  
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Solution 2

I Have Assign a value in connection String.....
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