Hello..I am developing a windows application in vb.net and getting an error of system.nullreference exception.
I am trying to insert data in the database, insertion occurs in the first go. But, when i stop the porgram and re-run, i get the exception. Can anybody please help me with this ? Here is the code :

Imports System.Data
Imports System.Data.OleDb
Imports System.EventArgs
Imports System.Data.OleDb.OleDbCommand
Imports System.Data.OleDb.OleDbConnection

Public Class ContactInfo_supp
Inherits System.Windows.Forms.Form

Dim Message As String
Dim cn As OleDbConnection
Dim cmd As OleDbCommand

Private Sub button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button3.Click

Try
'MsgBox("Open")
cn = New OleDbConnection("Provider=microsoft.jet.oledb.4.0;Data Source=E:\Project-Hemtech\HemDatabase1.mdb;")
cn.Open()
cmd = New OleDbCommand("insert into contactinfo(usertype,compname,compadd,compcity,comppin,compphcode,compph,compfaxcode,compfax,compmail,compsite,compregoff,compfact,products,interest,region,place,contper1,comprole1,compemail1,contnum1,ext1,mobnum1,contper2,comprole2,compemail2,contnum2,ext2,mobnum2,contper3,comprole3,compemail3,contnum3,ext3,mobnum3,weeklyoff,vat,cst,pan,ecc,commissionerate,range,division,servicetax,bankname,bankbranch,accnum,rtgs,instrname,modelnum,installdate,amc,callibration,period,expdate) values ('Supplier','" & textBox1.Text & "','" & textBox2.Text & "','" & textBox39.Text & "','" & textBox41.Text & "','" & textBox45.Text & "','" & textBox3.Text & "','" & textBox4.Text & "','" & textBox46.Text & "','" & textBox5.Text & "','" & textBox6.Text & "','" & textBox7.Text & "','" & textBox8.Text & "','" & textBox42.Text & "','" & textBox43.Text & "','" & ComboBox1.SelectedItem.ToString() & "','" & textBox44.Text & "','" & textBox9.Text & "','" & textBox10.Text & "','" & textBox47.Text & "','" & textBox11.Text & "','" & textBox12.Text & "','" & textBox13.Text & "','" & textBox18.Text & "','" & textBox17.Text & "','" & textBox48.Text & "','" & textBox16.Text & "','" & textBox15.Text & "','" & textBox14.Text & "','" & textBox23.Text & "','" & textBox22.Text & "','" & textBox49.Text & "','" & textBox21.Text & "','" & textBox20.Text & "','" & textBox19.Text & "','" & textBox50.Text & "','" & textBox25.Text & "','" & textBox26.Text & "','" & textBox27.Text & "','" & textBox28.Text & "','" & textBox29.Text & "','" & textBox30.Text & "','" & textBox31.Text & "','" & textBox32.Text & "','" & textBox33.Text & "','" & textBox34.Text & "','" & textBox35.Text & "','" & textBox36.Text & "','" & textBox37.Text & "','" & textBox38.Text & "','" & dateTimePicker1.Text & "','" & ComboBox2.SelectedItem.ToString() & "','" & ComboBox3.SelectedItem.ToString() & "','" & textBox40.Text & "','" & dateTimePicker2.Text & "')", cn)
cmd.ExecuteNonQuery()

MsgBox("Your Account Created Successfully ")

Dim f9 As New Action()
f9.Show()
Me.Hide()

Catch myException As Exception

MsgBox("No Record Inserted" + myException.ToString())

Finally
'MsgBox("Closing Connection")

cn.Close()
End Try

End Sub

At what line of code ur getting the error?

Imports System.Data
Imports System.Data.OleDb
Imports System.EventArgs
Imports System.Data.OleDb.OleDbCommand
Imports System.Data.OleDb.OleDbConnection

Public Class ContactInfo_supp
Inherits System.Windows.Forms.Form

Dim Message As String
Dim cn As OleDbConnection
Dim cmd As OleDbCommand



Private Sub button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button3.Click

Try
'MsgBox("Open")
cn = New OleDbConnection("Provider=microsoft.jet.oledb.4.0;Data Source=E:\Project-Hemtech\HemDatabase1.mdb;")
cn.Open()
cmd = New OleDbCommand("insert into contactinfo(usertype,compname,compadd,compcity,comppin,compphcode,compph,compfaxcode,compfax,compmail,compsite,compregoff,compfact,products,interest,region,place,contper1,comprole1,compemail1,contnum1,ext1,mobnum1,contper2,comprole2,compemail2,contnum2,ext2,mobnum2,contper3,comprole3,compemail3,contnum3,ext3,mobnum3,weeklyoff,vat,cst,pan,ecc,commissionerate,range,division,servicetax,bankname,bankbranch,accnum,rtgs,instrname,modelnum,installdate,amc,callibration,period,expdate) values ('Supplier','" & textBox1.Text & "','" & textBox2.Text & "','" & textBox39.Text & "','" & textBox41.Text & "','" & textBox45.Text & "','" & textBox3.Text & "','" & textBox4.Text & "','" & textBox46.Text & "','" & textBox5.Text & "','" & textBox6.Text & "','" & textBox7.Text & "','" & textBox8.Text & "','" & textBox42.Text & "','" & textBox43.Text & "','" & ComboBox1.SelectedItem.ToString() & "','" & textBox44.Text & "','" & textBox9.Text & "','" & textBox10.Text & "','" & textBox47.Text & "','" & textBox11.Text & "','" & textBox12.Text & "','" & textBox13.Text & "','" & textBox18.Text & "','" & textBox17.Text & "','" & textBox48.Text & "','" & textBox16.Text & "','" & textBox15.Text & "','" & textBox14.Text & "','" & textBox23.Text & "','" & textBox22.Text & "','" & textBox49.Text & "','" & textBox21.Text & "','" & textBox20.Text & "','" & textBox19.Text & "','" & textBox50.Text & "','" & textBox25.Text & "','" & textBox26.Text & "','" & textBox27.Text & "','" & textBox28.Text & "','" & textBox29.Text & "','" & textBox30.Text & "','" & textBox31.Text & "','" & textBox32.Text & "','" & textBox33.Text & "','" & textBox34.Text & "','" & textBox35.Text & "','" & textBox36.Text & "','" & textBox37.Text & "','" & textBox38.Text & "','" & dateTimePicker1.Text & "','" & ComboBox2.SelectedItem.ToString() & "','" & ComboBox3.SelectedItem.ToString() & "','" & textBox40.Text & "','" & dateTimePicker2.Text & "')", cn)
cmd.ExecuteNonQuery()

MsgBox("Your Account Created Successfully ")

Dim f9 As New Action()
f9.Show()
Me.Hide()

Catch myException As Exception

MsgBox("No Record Inserted" + myException.ToString())

Finally
'MsgBox("Closing Connection")

cn.Close()
End Try

End Sub

Please use code tags.. it will be easy to read.

Edited 5 Years Ago by Pgmer: n/a

Most propably is that one (or more) of the comboboxes has no SelectedItem.

By default, there is no SelectedItem on a combobox.

To verify if the combo has one, verify that the SelectedIndex value is greater than -1.

Also is a common good practice to verify that all the fields (tex boxes text, and combo boxes selected items ToString, etc.) does not contain an apostrophe before inserting them in a command.

Hope this helps.

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