vb.net and database(access)

[vb.netfreak]

i am trying to insert value using dataset but its giving me an error of null point exception(object was not created) at run time

'my code is

Dim cnCustomers As OleDbConnection

        cnCustomers = New OleDbConnection

        Try
            With cnCustomers
                '  If .State = ConnectionState.Open Then .Close()

                .ConnectionString = cnString
                .Open()
            End With
        Catch ex As OleDbException
            MsgBox(ex.ToString)
        End Try

        Dim dt As New DataTable
        dt = dsstudent.Tables("survey1")

      Dim dsnewRow As DataRow ---- giving error at this point 
            dsnewRow = dt.NewRow()

Error is :-(System.NullReferenceException)
tip is "Use the New keyword to create the instance. " at dim dt as new table

did it but not working

[G_Waddell]

What is dsStudent, I assume it is a dataset but I cant see you initialising it or declaring it. I se you opening a connection string then suddenly you're setting datatables....

[Reverend Jim]

The easiest way to insert a record into a table is by ADO as follows

Dim con As New ADODB.Connection
con.Open("Driver={SQL Server};Server=JIM-PC\SQLEXPRESS;Database=mydb;Trusted_Connection=yes;")

Dim query As String = "insert into Table1 (RegistrationNo,Field1,Field2) values(12,'John','Doe')"

con.Execute(query)
con.Close()

In this case I am inserting into a SQL Express 2008 table "Table1" in the database "mydb". That table has three fields named "RegistrationNo", "Field1" and "Field2".

[aerohn]

i am trying to insert value using dataset but its giving me an error of null point exception(object was not created) at run time

'my code is

Dim cnCustomers As OleDbConnection

cnCustomers = New OleDbConnection

Try
With cnCustomers
' If .State = ConnectionState.Open Then .Close()

.ConnectionString = cnString
.Open()
End With
Catch ex As OleDbException
MsgBox(ex.ToString)
End Try

Dim dt As New DataTable
dt = dsstudent.Tables("survey1")

Dim dsnewRow As DataRow ---- giving error at this point
dsnewRow = dt.NewRow()
Error is :-(System.NullReferenceException)
tip is "Use the New keyword to create the instance. " at dim dt as new table

did it but not working

It's better show us your code completely... You're using dsstudent without declaring it. And also your connectionString :)

[vb.netfreak]

i have already declared dsstudent as dataset but still not working!!

[vb.netfreak]

this is my code tell me where m wrong !!

Imports System.Data.OleDb
Public Class Form1
    Dim daCustomers As New OleDbDataAdapter()
    Dim dsstudent As New DataSet()
    Public Const cnString As String = "Provider=Microsoft.Jet.OLEDB.4.0;Persist Security Info=False;Data Source=E:\crawler\survey.mdb"
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim cnCustomers As OleDbConnection

        cnCustomers = New OleDbConnection

        Try
            With cnCustomers
                '  If .State = ConnectionState.Open Then .Close()

                .ConnectionString = cnString
                .Open()
            End With
        Catch ex As OleDbException
            MsgBox(ex.ToString)
        End Try

        Dim dt As New DataTable
        dt = dsstudent.Tables("survey1")

        If TextBox1.Text = "" Or TextBox3.Text = "" Then
            MsgBox("Please fill up ID or information.", MsgBoxStyle.Critical)

            Exit Sub
        End If


        ' If State = gModule.FormState.adStateAddMode Then
        Try   ' add a row

            Dim j As Integer
            Dim k As Integer = 0
            'Dim dsnewRow As DataRow = dsstudent.Tables("survey").NewRow
            Dim dsnewRow As DataRow
            dsnewRow = dt.NewRow()
            'dsnewRow
            For i = 1 To 10

                dsnewRow("ID") = TextBox1.Text
                dsnewRow("deptt") = TextBox3.Text
                dsnewRow("survey") = "1"
                dsnewRow("Question") = 1

                For j = 1 To 4
                    k = k + 1
                    If CType(Me.Controls.Find("RadioButton" & k, True)(0), RadioButton).Checked = True Then
                        dsnewRow("Answer") = CType(Me.Controls.Find("RadioButton" & j, True)(0), RadioButton).Text
                    End If
                Next j
                
                dt.Rows.Add(dsnewRow)

            Next i
           
            daCustomers.Update(dsstudent, "survey")

            MsgBox("Record successfully saved.", MsgBoxStyle.Information)
        Catch ex As OleDbException
            MsgBox(ex.ToString)
        End Try
    End Sub
    

End Class

[G_Waddell]

You have not populated the dataset so there are no tables in dsStudent.This is why you are getting an error tryng to use a table that does not exist. You must populate your dataset before using it.

You need to use an OLEDb Data adapter to populate your dataset.