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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=****");          
}
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);
}
 

Error is In this Line 4 -
con.Open();
 
Error is :- Cannot open Connection:System.NullReferenceException:Object Reference Not
set to an instance of an object.
Posted 28-Feb-13 16:43pm
Edited 28-Feb-13 20:21pm
v2
Comments
ZaneArellano at 1-Mar-13 1:23am
   
where did that con came from? your connection is named cn
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Solution 1

You have declared cn while declaring the connection object.
While using it, you have written con. Change it to cn and see if the error is still there.
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Solution 2

because declared cn so you should write cn.open()
write this...
try
           {
              cn.Open();
               str = "select *from DatabaseLogin where user_id='" + textBox2.Text + "'";
               com = new OleDbCommand(str, cn);
               OleDbDataReader reader = com.ExecuteReader();
               while (reader.Read())
               {
                   checkedListBox1.Items.Add(reader["stckdemge"]);
               }
 

 
           }
           catch (Exception ex)
           {
               MessageBox.Show(" " + ex);
           }
Happy Coding!
Smile | :)
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