private DataTable CreateCleanData()
{
    var cleanedDataTable = _loadedDataData.Copy();
    var columnsToKeep = new List<string>();
    columnsToKeep.Add(1.SelectedValue.ToString());
    columnsToKeep.Add(2.SelectedValue.ToString());
    columnsToKeep.Add(3.SelectedValue.ToString());
    columnsToKeep.Add(4.SelectedValue.ToString());
    columnsToKeep.Add(5.SelectedValue.ToString());
    columnsToKeep.Add(6.SelectedValue.ToString());

    for (var i = cleanedDataTable.Columns.Count - 1; i >= 0; i--)
        if (!columnsToKeep.Contains(cleanedDataTable.Columns[i].ColumnName))
            cleanedDataTable.Columns.Remove(cleanedDataTable.Columns[i]);
    cleanedDatTable.AcceptChanges();
    GC.Collect();

    return cleanedDataTable;
}