How do I programmatically determine the selected rows in a datagrid

The method DataGrid.IsSelected can tell you if a particular row is selected.
So, you could use IsSelected in a loop through all your rows to finds if
multiple rows have been selected. Depending upon the size of your datagrid,
this may be a viable solution. If not, you could track the selections
yourself by monitoring the key actions and the mouse actions. This would be
more work. Thanks to John Hughes to the suggestion to use the dataview.

[C#]
public ArrayList GetSelectedRows(DataGrid dg)
{
	ArrayList al = new ArrayList();
	CurrencyManager cm = (CurrencyManager)this.BindingContext[dg.DataSource, dg.DataMember];    
    	DataView dv = (DataView)cm.List;
    
	for(int i = 0; i < dv.Count; ++i)
	{
		if(dg.IsSelected(i))
			al.Add(i);
	}
	return al;
}

private void button1_Click(object sender, System.EventArgs e)
{
	string s = 'Selected rows:';
	foreach(object o in GetSelectedRows(dataGrid1))
	{
		s+=''+o.ToString();
	}
	MessageBox.Show(s);
}

[VB.NET]
	Public Function GetSelectedRows(ByVal dg As DataGrid) As System.Collections.ArrayList
		Dim al As New ArrayList()

		Dim cm As CurrencyManager = Me.BindingContext(dg.DataSource, dg.DataMember)
		Dim dv As DataView = CType(cm.List, DataView)
   
		Dim i As Integer
		For i = 0 to dv.Count - 1
			If dg.IsSelected(i) Then
				al.Add(i)
			End If
		End Next
		Return al
	End Function ’GetSelectedRows
	
	 Private Sub button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
		 Dim s As String = 'Selected rows:'
		Dim o As Object
		For Each o In GetSelectedRows(dataGrid1)
			s += ' ' + o.ToString()
		Next o
		MessageBox.Show(s)
	 End Sub ’button1_Click