hi to all:

I would like to delete all records in an field of my database and I have this code:

Code:
Dim sql1 As String
        
        Dim connection As New OleDb.OleDbConnection(String.Format("PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source = " & drive & IDempresa))
        connection.Open()
        
        Dim adapter As OleDb.OleDbDataAdapter

        sql1 = "select *" & _
        " from balancetegeral" & _
        " order by id"

        adapter = New OleDb.OleDbDataAdapter(sql1, connection)
        Dim commandbuilder As New OleDb.OleDbCommandBuilder(adapter)
        adapter.DeleteCommand = commandbuilder.GetDeleteCommand
        
        Dim dt As New DataTable
        adapter.Fill(dt)

        
        For Each r As DataRow In dt.Rows
            If r.Item("mensaisdebito") Then
                r.Delete()
            End If
        Next

        'Update database.  
        adapter.Update(dt)

        connection.Close()
In the instruction in bold I have this error:
Conversion from type 'DBNull' to type 'Boolean' is not valid.

Any help please

Thanks