I get this NullReferenceException

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C#

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.OleDb;
using System.Web.Security;

public partial class MasterPage : System.Web.UI.MasterPage
{
    string baglantistringi = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + HttpContext.Current.Server.MapPath("~/App_Data/KitapVT.accdb") + ";Persist Security info=false";
    public static OleDbConnection Baglanti;// access veri tabanına bağlantı nesnesi
    public static OleDbDataAdapter Adaptor;


    void sistemeGiris(string OturumKlasoru)
    {
        FormsAuthenticationTicket OturumBileti = new FormsAuthenticationTicket(1, txt_email.Text,
            DateTime.Now, DateTime.Now.AddMinutes(30), false, OturumKlasoru,
            FormsAuthentication.FormsCookiePath);
        string SifrelenmisBilet = FormsAuthentication.Encrypt(OturumBileti);
        HttpCookie cerez = new HttpCookie(FormsAuthentication.FormsCookieName, SifrelenmisBilet);
        if (OturumBileti.IsPersistent)
        {
            cerez.Expires = OturumBileti.Expiration;
        }
        Response.Cookies.Add(cerez);
        string GidilecekAdres = OturumKlasoru + "/Default.aspx";
        if (GidilecekAdres == null)
        {
            GidilecekAdres = "/Default.aspx";

        }
        Response.Redirect(GidilecekAdres, false);

    }
    protected void btnGiris_Click(object sender, EventArgs e)
    {
        string kullaniciTipi;
        string IP = Context.Request.ServerVariables["REMOTE_HOST"].ToString();
        DataTable dtGirisKontrol = new DataTable();
        string txt = "select * from kullanici where Sifre=@Sifre and Email=@Email";
        OleDbCommand cmd = new OleDbCommand(txt, Baglanti);
        cmd.Parameters.Add("@Sifre", OleDbType.Char, 100).Value = txt_sifre.Text;
        cmd.Parameters.Add("@Email", OleDbType.Char, 50).Value = txt_email.Text;
        Adaptor = new OleDbDataAdapter(cmd);
        if (Baglanti.State == ConnectionState.Closed)
        {// I get error right here(Null Reference Exception was unhandled by user code). 
            Baglanti.Open();

        }
        Adaptor.Fill(dtGirisKontrol);
        if (Baglanti.State == ConnectionState.Open)
        {
            Baglanti.Close();

        }
        if (dtGirisKontrol.Rows.Count == 0)
        {
            lblSonuc.Visible = true;
            lblSonuc.Text = "Kullanici adi veya şifreniz hatalı";
            return;
        }
        else
        {
            try
            {
                Session.Timeout = 30;
                Session["Email"] = txt_email.Text;
                Session["IDKullanici"] = dtGirisKontrol.Rows[0]["IDKullanici"].ToString();
                Session["KullaniciTipi"] = dtGirisKontrol.Rows[0]["KullaniciTipi"].ToString();
                kullaniciTipi = dtGirisKontrol.Rows[0]["KullaniciTipi"].ToString();
                Session["AdiSoyadi"] = dtGirisKontrol.Rows[0]["AdiSoyadi"].ToString();
                Session["IP"] = IP;

                if (kullaniciTipi == "ADMIN")
                {
                    sistemeGiris("uAdmin");

                }
                else if (kullaniciTipi == "UYE")
                {
                    sistemeGiris("uUYE");
                }
            }
            catch (Exception ex)
            {
                lblSonuc.Text = ex.Message.ToString();
            }
        }


        
    }
}

How can fix this code?

Posted 17-Dec-13 8:09am

XaxPRoy

Updated 17-Dec-13 8:27am

N_tro_P

v2

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Comments

joginder-banger 17-Dec-13 14:27pm

I think you can't provide a memory your Baglanti <pre lang="c#">Baglanti.State</pre>
you can used the public OleDbConnection Baglanti= new OleDbConnection();

XaxPRoy 17-Dec-13 14:38pm

No still doesn't work but thanks.

Matt T Heffron 17-Dec-13 14:47pm

Baglanti doesn't appear to be initialized anywhere, so it is null.
You must assign a value to Baglanti before it is referenced, as joginder-banger indicated, above.
Change to:
public static OleDbConnection Baglanti= new OleDbConnection();

2 solutions

Solution 2

just write you whole code in try catch block and give some exception error msg in catch block and one by one check alll values you can easily find it

Posted 17-Dec-13 21:31pm

Gaurav Makwana

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OriginalGriff · Accepted Answer · 2013-12-17T08:50:00

You declare an OdbcConnection variable (Baglanti), but you don't create an instance of the class:

C#

public static OleDbConnection Baglanti;// access veri tabanına bağlantı nesnesi

The only other reference to Baglanti in your code is when you use it in btnGiris_Click

You need to assign an instance to the variable, probably at the top of the method:

C#

    protected void btnGiris_Click(object sender, EventArgs e)
    {
        string kullaniciTipi;
        Baglanti = new OleDbConnection(baglantistringi);   //**** ADD THIS
...
        if (Baglanti.State == ConnectionState.Open)
        {
            Baglanti.Close();
            Baglanti = null;                               //**** ADD THIS
...

}