How to disable highlighting of a selected item in combobox uisng C#

The simplest method to use is to pass the focus from your combobox to another control. for an example you can place the following code in the combo box selection change event, assuming you have another combobox:

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    comboBox2.Focus();
}

Another simple method is to place the following code in your forms Paint event.

private void myForm_Paint(object sender, PaintEventArgs e)
{
    comboBox1.SelectionLength = 0;
}

There really isn't a built in method for doing what you ask and I've seen numerous work arounds that become rather large for such a simple effect. The methods above are what I would use.

Good luck.