c# – 是什么导致系统发出蜂鸣声？

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

    }

一旦我按下输入而不是代码中的其他行,就会发生这种情况.关于我缺少什么的想法？

这是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;
        }

    }