/ using vb.net 2010
/using m.s access database
i already finish my program and the program works perfectly by using a single table in Microsoft Access. but when i tried to add a new table and set a value accordingly.
error occured : Object reference not set to an instance of an object. NullReferenceException was unhandled.
/ form code
dssNewRow = ds.Tables("tblstudentsecond").NewRow() - error................
/modconnection
if you want to see my program here's the file link :
http://www.mediafire.com/#08pb7jtz807gl
/using m.s access database
i already finish my program and the program works perfectly by using a single table in Microsoft Access. but when i tried to add a new table and set a value accordingly.
error occured : Object reference not set to an instance of an object. NullReferenceException was unhandled.
/ form code
dssNewRow = ds.Tables("tblstudentsecond").NewRow() - error................
Code:
Imports System.Data.OleDb
Public Class Form1
Dim inc As Integer
Dim maxrows As Integer
Dim picPath As String
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
get_student()
connection()
sql = "Select * From tblstudent"
da = New OleDb.OleDbDataAdapter(sql, con)
da.Fill(ds, "tblstudent")
con.Close()
maxrows = ds.Tables("tblstudent").Rows.Count
inc = 0
End Sub
Private Sub NavigateRecords()
On Error Resume Next
txtid.Text = ds.Tables("tblstudent").Rows(inc).Item(0)
txtlname.Text = ds.Tables("tblstudent").Rows(inc).Item(1)
txtfname.Text = ds.Tables("tblstudent").Rows(inc).Item(2)
txtmi.Text = ds.Tables("tblstudent").Rows(inc).Item(3)
txtaddress.Text = ds.Tables("tblstudent").Rows(inc).Item(4)
txtloanamount.Text = ds.Tables("tblstudentsecond").Rows(inc).Item(0)
txtinterest.Text = ds.Tables("tblstudentsecond").Rows(inc).Item(1)
txtyears.Text = ds.Tables("tblstudentsecond").Rows(inc).Item(2)
txtmonthlypayment.Text = ds.Tables("tblstudentsecond").Rows(inc).Item(3)
connection()
sql = "SELECT * From tblstudent WHERE id ='" & txtid.Text & "'"
cmd = New OleDbCommand(Sql, con)
dr = cmd.ExecuteReader()
If dr.Read Then
picStudent.Image = Image.FromFile(Application.StartupPath & "\Images\" & dr("stud_pic"))
End If
con.Close()
End Sub
Private Sub btnnext_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnnext.Click
If inc <> maxrows - 1 Then
inc = inc + 1
NavigateRecords()
Else
MsgBox("No More Records found", MsgBoxStyle.Exclamation, "Next")
End If
End Sub
Private Sub btnprev_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnprev.Click
If inc > 0 Then
inc = inc - 1
NavigateRecords()
Else
MsgBox("You hit the First Record", MsgBoxStyle.Exclamation, "Prev")
End If
End Sub
Private Sub btnfirst_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnfirst.Click
If inc <> 0 Then
inc = 0
NavigateRecords()
End If
End Sub
Private Sub btnlast_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnlast.Click
If inc <> maxrows - 1 Then
inc = maxrows - 1
NavigateRecords()
End If
End Sub
Private Sub btnupdate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnupdate.Click
Dim cb As New OleDb.OleDbCommandBuilder(da)
' Dim cb As SqlCommandBuilder
' cb = New SqlCommandBuilder(da)
' ds.Tables("tblstudent").Rows(inc).Item("ID") = txtid.Text
ds.Tables("tblstudent").Rows(inc).Item("Lname") = txtlname.Text
ds.Tables("tblstudent").Rows(inc).Item("Fname") = txtfname.Text
ds.Tables("tblstudent").Rows(inc).Item("Mi") = txtmi.Text
ds.Tables("tblstudent").Rows(inc).Item("Address") = txtaddress.Text
dss.Tables("tblstudentsecond").Rows(inc).Item("LoanAmount") = txtloanamount.Text
dss.Tables("tblstudentsecond").Rows(inc).Item("Interest") = txtinterest.Text
dss.Tables("tblstudentsecond").Rows(inc).Item("Years") = txtyears.Text
dss.Tables("tblstudentsecond").Rows(inc).Item("MonthlyPayment") = txtmonthlypayment.Text
da.Update(ds, "tblstudent")
da.Update(dss, "tblstudentsecond")
MsgBox("Data updated")
End Sub
Private Sub btnaddnew_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnaddnew.Click
btncommit.Enabled = True
btnaddnew.Enabled = False
btnupdate.Enabled = False
btndelete.Enabled = False
txtid.Clear()
txtfname.Clear()
txtlname.Clear()
txtmi.Clear()
txtaddress.Clear()
txtloanamount.Clear()
txtinterest.Clear()
txtyears.Clear()
txtmonthlypayment.Clear()
txtid.Focus()
End Sub
Private Sub btncancel_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btncancel.Click
btncommit.Enabled = False
btnaddnew.Enabled = True
btnupdate.Enabled = True
btndelete.Enabled = True
inc = 0
NavigateRecords()
End Sub
Private Sub btncommit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btncommit.Click
If inc <> -1 Then
Dim cb As New OleDb.OleDbCommandBuilder(da)
Dim picfaculty As String
Dim FileToCopy As String
Dim NewCopy As String
FileToCopy = picPath
NewCopy = Application.StartupPath & "\Images\" & lblPicName.Text
If System.IO.File.Exists(FileToCopy) = True Then
System.IO.File.Copy(FileToCopy, NewCopy)
picfaculty = lblPicName.Text
Else
picfaculty = "pic.png"
End If
Dim dsNewRow, dssNewRow As DataRow
dsNewRow = ds.Tables("tblstudent").NewRow()
dssNewRow = ds.Tables("tblstudentsecond").NewRow()
'ds.Tables("tblstudent").NewRow()
dsNewRow.Item("ID") = txtid.Text
dsNewRow.Item("Lname") = txtlname.Text
dsNewRow.Item("Fname") = txtfname.Text
dsNewRow.Item("Mi") = txtmi.Text
dsNewRow.Item("Address") = txtaddress.Text
dssNewRow.Item("LoanAmount") = txtloanamount.Text
dssNewRow.Item("Interest") = txtinterest.Text
dssNewRow.Item("Years") = txtyears.Text
dssNewRow.Item("MonthlyPayment") = txtmonthlypayment.Text
ds.Tables("tblstudent").Rows.Add(dsNewRow)
ds.Tables("tblstudentsecond").Rows.Add(dsNewRow)
da.Update(ds, "tblstudent")
da.Update(dss, "tblstudentsecond")
MsgBox("New Record added to the Database", MsgBoxStyle.Information, "Save")
btncommit.Enabled = False
btnaddnew.Enabled = True
btnupdate.Enabled = True
btndelete.Enabled = True
get_student()
End If
' da.Update(ds, "tblstudent")
End Sub
Private Sub btndelete_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btndelete.Click
Dim cb As New OleDb.OleDbCommandBuilder(da)
' Dim cb As SqlCommandBuilder
' cb = New SqlCommandBuilder(da)
ds.Tables("tblstudent").Rows(inc).Delete()
maxrows = maxrows - 1
inc = 0
NavigateRecords()
da.Update(ds, "tblstudent")
End Sub
Private Sub btnUpload_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
Dim dlg As OpenFileDialog = New OpenFileDialog()
Dim res As DialogResult = dlg.ShowDialog()
With dlg
.Filter = "All Image File (*.jpg;*.bmp;*.gif;*.png)|*.jpg;*.bmp;*.gif;*.png"
.Title = "All Image File"
End With
If res = Windows.Forms.DialogResult.OK Then
Dim str As String()
str = Split(dlg.FileName, "\")
For Each c As String In str
If c.EndsWith(".jpg") Or c.EndsWith(".jpeg") Or c.EndsWith(".png") Or c.EndsWith(".gif") Or c.EndsWith(".bmp") Or c.EndsWith(".JPG") Or c.EndsWith(".JPEG") Or c.EndsWith(".PNG") Or c.EndsWith(".GIF") Or c.EndsWith(".BMP") Then
lblPicName.Text = c
picPath = dlg.FileName
picStudent.Image = Image.FromFile(picPath)
End If
Next
End If
End Sub
Private Sub get_student()
Try
lvstudent.Items.Clear()
connection()
sql = "SELECT * From tblstudent order by id asc"
cmd = New OleDbCommand(sql, con)
dr = cmd.ExecuteReader
While dr.Read
Dim lv As ListViewItem = lvstudent.Items.Add(dr("id"))
With lv.SubItems
.Add(dr("Lname"))
.Add(dr("Fname"))
.Add(dr("Mi"))
.Add(dr("Address"))
End With
End While
con.Close()
Catch ex As Exception
'MessageBox.Show(ex.ToString())
End Try
End Sub
Private Sub view_student()
connection()
listselect = lvstudent.SelectedItems.Item(0).Text
sql = "SELECT * From tblstudent WHERE id ='" & listselect & "'"
cmd = New OleDbCommand(sql, con)
dr = cmd.ExecuteReader()
If dr.Read Then
txtid.Text = dr("ID")
txtlname.Text = dr("Lname")
txtfname.Text = dr("Fname")
txtmi.Text = dr("Mi")
txtaddress.Text = dr("Address")
lblPicName.Text = dr("stud_pic")
picStudent.Image = Image.FromFile(Application.StartupPath & "\Images\" & dr("stud_pic"))
End If
con.Close()
End Sub
Private Sub lvstudent_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles lvstudent.Click
Call view_student()
End Sub
Private Sub btnClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClose.Click
Me.Close()
End Sub
Private Sub btnSearch_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSearch.Click
Dim search As String
search = InputBox("Please input id to search..", "Search")
lvstudent.Items.Clear()
connection()
sql = "SELECT * From tblstudent where id = '" & search & "'"
cmd = New OleDbCommand(sql, con)
dr = cmd.ExecuteReader
While dr.Read
Dim lv As ListViewItem = lvstudent.Items.Add(dr("id"))
With lv.SubItems
.Add(dr("Lname"))
.Add(dr("Fname"))
.Add(dr("Mi"))
.Add(dr("Address"))
End With
End While
con.Close()
End Sub
Private Sub btnrefresh_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnrefresh.Click
Call get_student()
End Sub
Private Sub btncalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btncalculate.Click
Dim loan_am, interest_ra, payment_1 As Double
Dim num_years As Integer
loan_am = CDbl(txtloanamount.Text.Trim)
interest_ra = CDbl(txtinterest.Text.Trim)
If interest_ra > 1 Then interest_ra = interest_ra / 100
num_years = CInt(txtyears.Text.Trim)
payment_1 = Pmt(interest_ra / 12, num_years * 12, -1 * loan_am)
txtmonthlypayment.Text = Format(payment_1, "P#,##0.00")
End Sub
End ClassCode:
Imports System.Data.OleDb
Module modConnection
Public sql, listselect As String
Public ds, dss As New DataSet
Public da As New OleDb.OleDbDataAdapter
Public cmd As New OleDb.OleDbCommand
Public dr As OleDb.OleDbDataReader
Public con As New OleDb.OleDbConnection
Public dbProvider As String
Public dbSource As String
Public Sub Connection()
Try
dbProvider = "PROVIDER=Microsoft.ACE.OLEDB.12.0;"
dbSource = "Data Source = D:\database\tblstudent.accdb"
con.ConnectionString = dbProvider & dbSource
con.Open()
Catch ex As Exception
MsgBox(Err.Description, MsgBoxStyle.Critical, "Database Path Error")
End Try
End Sub
End Modulehttp://www.mediafire.com/#08pb7jtz807gl