validate entered data befor apply it to BindingSource underlying source
<pre><code>BindingSource BS = new BindingSource();
public Cource()
{
    InitializeComponent();
}

private void Cource_Load(object sender, EventArgs e)
{
    DataSet ds = new DataAccess.newCourcesDAC().GetAllTeachers();
    BS.DataSource = ds;
    BS.DataMember = "tblCourses";
    dataGridView1.DataSource = BS;
    txtCourseID.DataBindings.Add("Text", BS, "CourseID");
    txtCourseName.DataBindings.Add("Text", BS, "CourseName");
    txtPrequest.DataBindings.Add("Text", BS, "Prequest");
    txtCourseContent.DataBindings.Add("Text", BS, "CourseContent");
}

private void btnAdd_Click(object sender, EventArgs e)
{
    BS.AddNew();
}
</code></pre>

<p>I have a datasource with a datatable called "tblCourses" that have 4 columns.
I use a BindingSource to manage currency beetwen datagridView and 4 text box.
i use addNew metode of bindingSource to add new row to dataTable .
how can i validate entered data befor apply it to BindingSource underlying source?</p>
