Please Help solve null reference exception

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C#

public void FillDT()
       {
           OleDbConnectionStringBuilder sb=null;
           SaveFileDialog sfd = new SaveFileDialog();
           if (sb == null||sb.DataSource!=null||sfd.FileName!=null)
           {
               sb.DataSource =sfd.FileName;
               return;
           }

           bookConn = new OleDbConnection(sb.DataSource=sfd.FileName);
           bookConn.Open();
           oleDbCmd.Connection = bookConn;

           oleDbCmd.CommandText = "INSERT INTO students (Firstname,Lastname,Age,Gender,School,Gfirstname,Glastname,Contact,Occupation,PostalAddr) Values('" + this.FirstnameTB.Text + "','" + this.LastnameTB.Text + "','" + this.AgeTB.Text + "','" + this.GenderTB.Text + "','" + this.SchoolTB.Text + "','" + this.GFirstnameTB.Text + "','" + this.GLastnameTB.Text + "','" + this.ContactTB.Text + "','" + this.OccupationTB.Text + "','" + this.AddressTB.Text + "');";
           int temp = oleDbCmd.ExecuteNonQuery();

           if (temp > 0)
           {
               FirstnameTB.Text = null;
               LastnameTB.Text = null;
               AgeTB.Text = null;
               GenderTB.Text = null;
               SchoolTB.Text = null;
               GFirstnameTB.Text = null;
               GLastnameTB.Text = null;
               ContactTB.Text = null;
               OccupationTB.Text = null;
               AddressTB.Text = null;
               MessageBox.Show("Record Successfuly Added", "Entry Added");
           }
           else
           {
               MessageBox.Show("Failed to Add Record", "Entry failure");
           }
           bookConn.Close();
       }

The exception occurs at "sb.DataSource= sfd.FileName;"

Posted 8-Jan-13 0:46am

Member 9430088

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OriginalGriff · Answer 1 · 2013-01-08T01:07:00

Ehem :cough:

C#

OleDbConnectionStringBuilder sb=null;
SaveFileDialog sfd = new SaveFileDialog();
if (sb == null||sb.DataSource!=null||sfd.FileName!=null)
{
    sb.DataSource =sfd.FileName;
    return;
}

sb is null - you set it to it, so the test will always pass on the first test (the others will not be done)
Perhaps you meant

C#

if (sb != null||sb.DataSource!=null||sfd.FileName!=null)

But in that case, it will always fail...

prashant patil 4987 · Answer 2 · 2013-01-08T01:13:00

try to add check your condition

C#

OleDbConnectionStringBuilder sb=null;
            SaveFileDialog sfd = new SaveFileDialog();
            if (sb == null||sb.DataSource!=null||sfd.FileName!=null)
            {
                sb.DataSource =sfd.FileName;
                return;
            }

In above code your sb is always Null so that if "sfd.FileName == Null or Not Null" does meant. due to || (Or Condition in if ). so try to chenge your condition like below

C#

OleDbConnectionStringBuilder sb=null;
            SaveFileDialog sfd = new SaveFileDialog();
            if ((sb == null||sb.DataSource!=null) && (sfd.FileName!=null))
            {
                sb.DataSource =sfd.FileName;
                return;
            }

Rahul Rajat Singh · Answer 3 · 2013-01-08T01:14:00

You have not allocated memory for the OleDbConnectionStringBuilder variable sb

C#

OleDbConnectionStringBuilder sb=null;
           SaveFileDialog sfd = new SaveFileDialog();
           if (sb == null||sb.DataSource!=null||sfd.FileName!=null)
           {
               sb = new OleDbConnectionStringBuilder();
               sb.DataSource =sfd.FileName;
               return;
           }

tarun1991 · Answer 4 · 2013-01-08T01:50:00

Solution 4

use of try catch statement. It also remind the user to fill the required place or leave the catch block, if you don't want to show any message.

Posted 8-Jan-13 1:50am

tarun1991

Please Help solve null reference exception

4 solutions

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