Object Reference Null in Connection Property

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Error is In this Line

VB

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...

C#

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 1:02am

kashifjaat

Updated 28-Feb-13 1:10am

Chris Maunder772.8K

v2

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S.P.Tiwari 28-Feb-13 7:08am

where u created connection object? and assign the connection string. give more details..

kashifjaat 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

2 solutions

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Hrushikesh_phapale · Answer 1 · 2013-02-28T18:38:00

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="); }

C#

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);
           }

OriginalGriff · Answer 2 · 2013-02-28T01:07:00

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:

C#

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:

C#

con = new OleDbConnection(strConnect);

Object Reference Null in Connection Property

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