How to use treeview to filter datagridview

// The method applies to all treeviews

foreach(TreeNode node in treeView1.Nodes) // Root treeview
            {
                if(node.Nodes.Count > 0)
                {
   // Iterate through the children nodes to start building the rowFilter string
                    foreach(TreeNode childNode in node.Nodes)
                    {
                        if (childNode.Checked)
                        {
                            if(treeview1.Length > 0)
                            {
                                treeview1RowFilter += " OR ";
                            }
                            treeview1RowFilter += "[AreaCode] = " + childNode.Text;
                        }
                        else if(childNode.Checked)
                        {
                            MessageBox.Show("Combobox is empty");
                        }
                    }
                }
            } 
// The same foreach loop for two remaining treeview
......
//  rowFilter strings that will have to concantenate 
 string rowFilter = string.Empty;

        if (cb11.Checked)
        {
            rowFilter += " [AreaCode] = " + cb11.Text.Trim();
        }
        if (cb16.Checked)
        {
            if (rowFilter.Length > 0)
                rowFilter += " OR";
            rowFilter += " [AreaCode] = " + cb16.Text.Trim();
        }
        if (cb31.Checked)
        {
            if (rowFilter.Length > 0)
                rowFilter += " OR";
            rowFilter += " [AreaCode] = " + cb31.Text.Trim();
        }

rowFilter = "(Grant='Yes') AND (AreaCode = 11 OR AreaCode = 31) AND (Land='North' OR Land='Schweiz')";

        try
        {
            //Check an see what's in the dgv
            DataView dv = new DataView(dt);
            dv.RowFilter = rowFilter;
            datagridview.Datasource = dv;
        }
        catch (Exception)
        {
            MessageBox.Show("Can’t find the column", "Info", MessageBoxButtons.OK, MessageBoxIcon.Information);
        }