login form code help usig ms access database

hi i am new to c# and wondering if you could help me solve the problem to my login function for my website thanks

Code:

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protected void btnlogin_Click(object sender, EventArgs e)
        {
            OleDbConnection con = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=CWsystem.mdb");
          //  OleDbConnection con = new OleDbConnection(ConfigurationManager.ConnectionStrings["CWsystem.mdb"].ConnectionString);
            con.Open();
            string cmdStr="select count(*) from Person where UserID='" + txtusername.Text + "'";
            OleDbCommand Checkuser=new OleDbCommand(cmdStr, con);
            int temp = Convert.ToInt32(Checkuser.ExecuteScalar().ToString());
            if(temp== 1)
            {
                    string cmdStr2="Select Password from Person where username='" + txtusername.Text + "'";
                OleDbCommand pass=new OleDbCommand(cmdStr2, con);
                string password=pass.ExecuteScalar().ToString();
                con.Close();

                if(password == txtpassword.Text)
                {
                    Session["New"] = txtusername.Text;
                    Response.Redirect("university.aspx");
                }
                else
                {
                    Label1.Visible = true;
                    Label1.Text = "invalid password";
                }
            }
                else
                {
                    Label1.Visible = true;
                    Label1.Text = "invalid password";
                }

            }

        protected void txtpassword_TextChanged(object sender, EventArgs e)
        {

        }
        }
    }

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Put a breakpoint on the line if(temp== 1) and start debugging the site by pressing F5. Then single-step through the code and look values of the variables. Are your queries returning what you expect?

Could not find file 'C:\Program Files (x86)\Common Files\Microsoft Shared\DevServer\10.0\CWsystem.mdb'.

don't seem to reconise my database

which happens at con.Open();

Is the database located at that location? Is the path valid?

Keep in mind that your connection string is

Code:

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OleDbConnection con = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=CWsystem.mdb");

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Which means it expects the CWSystem.mdb file to be located in the same file directory as your program .exe.

If the cwsystem.mdb is listed as a file in the visual studio project, right click on it an choose properties. Change the 'Copy to output directory' property to 'Copy always'. One caveat to doing this is that any changes you make to your database won't be persisted between debug sessions of your application (because every time you compile and debug the app, a new copy of the mdb gets put in the output directory).

{"Object reference not set to an instance of an object."}

OleDbConnection con = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=J:\enterprise web develop\enterprise\CWsystem.mdb");

this is the same directory as where the database is in the data_app section and the connection to the database is working

Quote:

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Originally Posted by dekon

{"Object reference not set to an instance of an object."}

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Where does this error occur? have you single stepped through the code in a debugger to find the line that throws this error?

Quote:

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Originally Posted by dekon

OleDbConnection con = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=J:\enterprise web develop\enterprise\CWsystem.mdb");

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You may have to escape the backslashes in this code as follows:

Code:

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OleDbConnection con = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=J:\\enterprise web develop\\enterprise\\CWsystem.mdb");

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int temp = Convert.ToInt32(Checkuser.ExecuteScalar().ToString());

data type mismatch

and thanks was finally able to establish a connection