What is causing a system beep?

Question

This is what I'm using to allow the enter button to start the search. It works but causes a system beep. I have no idea why.

    private void searchbox_KeyUp(object sender, KeyEventArgs e)
    {
        if (e.KeyCode == Keys.Enter)
        {
            searchbutton.PerformClick();
        }
        else
        {
            //Run.
        }

    }

It happens as soon as I press enter and not some other line in the code. Thoughts on what I'm missing?

Here is searchbutton_Click:

    private void searchbutton_Click(object sender, EventArgs e)
    {
        var searchvar = searchbox.Text;
        SqlParameter var1 = new SqlParameter(@"var1", SqlDbType.Text);
        var1.Value = "%" + searchvar + "%";
        var conn = new SqlConnection("Data Source=TX-MANAGER;Initial Catalog=Contacts;Integrated Security=True");
        var comm = new SqlCommand(@"SELECT [Name ID], First, Last, Address, City, State, ZIP FROM contacts WHERE (First LIKE @var1) OR (Last LIKE @var1)", conn);
        if (checkBox1.Checked == true)
        {
            comm.CommandText += "ORDER BY ZIP";
        }
        else
        {
            //Run.
        }
        try
        {
            comm.Parameters.Add(var1);
            conn.Open();
            comm.CommandType = CommandType.Text;
            SqlDataAdapter da = new SqlDataAdapter(comm);
            DataTable dt = new DataTable();
            da.Fill(dt);
            dataGridView1.DataSource = dt;
            conn.Close();
        }
        catch (Exception e1)
        {
            display_box.Text = e1.ToString();
            tabControl1.Focus();
        }
        finally
        {
            int rowcount = dataGridView1.RowCount - 1;
            count.Text = rowcount.ToString();
            tabControl1.SelectedTab = tabPage2;
        }

    }

Answer 1

You could try adding e.Handled = true; to the KeyPressed event for your TextBox.

Normally, if your Form doesn't have its AcceptButton property set, a system beep is played when hitting Enter inside a TextBox. The beep indicates that there's no default button defined for your Form.

Answer 2

Add the following event handler (in addition to KeyUp):

private void searchbox_KeyPress(object sender, KeyPressEventArgs e)
{
    if (e.KeyChar == '\r')
        e.Handled = true;
}

That is, subscribe to the KeyPress event and when Enter is pressed, set e.Handled to true. I just tested this on my machine and it worked; it removed the beep.