problem with editing/updating my program in visual basic

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VB

Visual-Studio

Hi, I am having a problem with editing/updating my program in visual basic. It does not seem to update my access database.

Can someone please assist me?

This is an error I get when trying to UPDATE a field :
"An unhandled exception of type 'System.Data.OleDb.OleDbException' occurred in BMS College.exe

Additional information: The record cannot be deleted or changed because table 'ASSESMENT' includes related records."

Also when I click the SAVE button, the data does not get added to the ACCESS Database.

This is the code for one of my forms :

Dim cnn As New OleDb.OleDbConnection

    Private Sub HelpToolStripMenuItem1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles HelpToolStripMenuItem1.Click
        MessageBox.Show("Please consult our Teckies.")
    End Sub

    Private Sub AboutToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles AboutToolStripMenuItem.Click
        About.ShowDialog()
    End Sub

    Private Sub ToolStripTextBox1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ToolStripTextBox1.Click
        First_form.Close()

    End Sub

    Private Sub ClearToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ClearToolStripMenuItem.Click
        Me.STUD_IDTextBox.Text = " "
        Me.STUD_FNAMETextBox.Text = " "
        Me.STUD_LNAMETextBox.Text = " "
        Me.MEN_IDTextBox.Text = " "
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'TODO: This line of code loads data into the 'Access_database_of_BMSDataSet1.Students' table. You can move, or remove it, as needed.
        Me.StudentsTableAdapter1.Fill(Me.Access_database_of_BMSDataSet1.Students)
        'TODO: This line of code loads data into the 'Access_database_of_BMSDataSet.Students' table. You can move, or remove it, as needed.
        Me.StudentsTableAdapter1.Fill(Me.Access_database_of_BMSDataSet1.Students)
        ''cnn = New OleDb.OleDbConnection
        ''cnn.ConnectionString("provider'microsoft.jet.oledb.4.0;datasource'" & Application.StartupPath & "\data.mdb"



    End Sub

    Private Sub Exit3btn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Exit3btn.Click
        Me.Close()
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnAdd.Click
        ''Dim cmd As New OleDb.OleDbCommand
        ''cnn.ConnectionString
        Me.Validate()
        Me.StudentsBindingSource.EndEdit()
        Me.TableAdapterManager.UpdateAll(Me.Access_database_of_BMSDataSet1)

    End Sub

    Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click
        Me.STUD_IDTextBox.Text = " "
        Me.STUD_FNAMETextBox.Text = " "
        Me.STUD_LNAMETextBox.Text = " "
        Me.MEN_IDTextBox.Text = " "
    End Sub

    Private Sub StudentsBindingNavigatorSaveItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
        Me.Validate()
        Me.StudentsBindingSource.EndEdit()
        Me.TableAdapterManager.UpdateAll(Me.Access_database_of_BMSDataSet1)

    End Sub


    Private Sub BtnEdit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnEdit.Click
        Me.Validate()
        Me.StudentsBindingSource.AddNew()
        Me.TableAdapterManager.UpdateAll(Me.Access_database_of_BMSDataSet1)
    End Sub

    Private Sub Btndelete_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Btndelete.Click
        MsgBox("You are about to delete this record...", MsgBoxStyle.OkOnly)
        Me.Validate()
        Me.StudentsBindingSource.RemoveCurrent()
        Me.TableAdapterManager.UpdateAll(Me.Access_database_of_BMSDataSet1)
    End Sub



    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        Dim str As String = TextBox1.Text
        Try
            If Me.TextBox1.Text.Trim(" ") = " " Then
            Else
                For i As Integer = 0 To StudentsDataGridView.Rows.Count - 1
                    For j As Integer = 0 To Me.StudentsDataGridView.Rows(i).Cells.Count - 1
                        If StudentsDataGridView.Item(j, i).Value.ToString().ToLower.StartsWith(str.ToLower) Then
                            StudentsDataGridView.Rows(i).Selected = True
                            StudentsDataGridView.CurrentCell = StudentsDataGridView.Rows(i).Cells(j)
                            Exit Try
                        End If
                    Next
                Next i
            End If
        Catch abc As Exception
            MessageBox.Show("Error : No Student Found!")
        End Try
    End Sub


    Private Sub btnvp_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnvp.Click
        Student_Information.Show()
    End Sub
End Class