Question

i have application with Combobox who show all the network adapter on my machine and when the application start-up i want that the default intem in my Combobox will marked, how can i do it ?

private void Form1_Load(object sender, EventArgs e)
{
    List<myAdapters> res = adapters.getAdapters();
    comboBoxAdapters.Items.AddRange(res.ToArray());
    comboBoxAdapters.SelectedIndex = 0;
}

Answer 1

Do you mean setting the first value as selected

comboBoxAdapters.SelectedItem = comboBoxAdapters.Items[0];

From the comments i feel you need to set the ActiveControl of the form as the combobox

this.ActiveControl = comboBoxAdapters;