try
private void Form1_Load(object sender, EventArgs e)
{
foreach (TabPage tab in tabControl1.Controls)
{
foreach (Label lbl in tab.Controls.OfType<Label>())
{
lbl.MouseEnter += lbl_MouseEnter;
lbl.MouseLeave += lbl_MouseLeave;
}
}
}
void lbl_MouseLeave(object sender, EventArgs e)
{
Label lbl = (Label)sender;
lbl.Font = new Font(lbl.Font.Name, 10, FontStyle.Regular);
}
void lbl_MouseEnter(object sender, EventArgs e)
{
Label lbl = (Label)sender;
lbl.Font = new Font(lbl.Font.Name, 10, FontStyle.Bold);
}