搜索后使用TextChanged事件重置Listview的背景颜色

Question

I have a textbox that I can use to search for items and subitems in a listview. Once matches are found the BG colour of the items changes. This works fine, but when I delete the entry from the textbox the items and subitems still remain highlighted until I enter another search.
I am not sure if it is the event that I am using or if it is a problem with my logic. I want the items to be highlighted dynamically as the user types in the search but if they delete the entry I want the BG colour to change back to white.

private void txtSearchMenu_TextChanged(object sender, EventArgs e)
    {
        string searchVal = txtSearchMenu.Text.ToLower();
        if (searchVal != "")
        {
            foreach (ListViewItem item in lvMenuItems.Items)
            {
                foreach (ListViewItem.ListViewSubItem subSearch in item.SubItems)
                {
                    if (subSearch.Text.ToLower().Contains(searchVal) == true)
                    {
                        subSearch.BackColor = Color.MediumAquamarine;
                    }
                    else
                    {
                        subSearch.BackColor = Color.White;
                    }
                }
                item.UseItemStyleForSubItems = false;
            }
        }
    }

Answer 1

As Sintar said:

private void txtSearchMenu_TextChanged(object sender, EventArgs e)
{
    string searchVal = txtSearchMenu.Text.ToLower();
    if (searchVal != "")
    {
        foreach (ListViewItem item in lvMenuItems.Items)
        {
            foreach (ListViewItem.ListViewSubItem subSearch in item.SubItems)
            {
                if (subSearch.Text.ToLower().Contains(searchVal) == true)
                {
                    subSearch.BackColor = Color.MediumAquamarine;
                }
                else
                {
                    subSearch.BackColor = Color.White;
                }
            }
            item.UseItemStyleForSubItems = false;
        }
    }
    else
    {
        foreach (ListViewItem item in lvMenuItems.Items)
        {
            foreach (ListViewItem.ListViewSubItem subSearch in item.SubItems)
            {
                subSearch.BackColor = Color.White;
            }
        }
    }
}

Answer 2

when I delete the entry from the textbox the items and subitems still remain highlighted until I enter another search

This is because you do nothing if textbox is blank.

Move check for empty string inside foreach like this:

private void txtSearchMenu_TextChanged(object sender, EventArgs e)
{
    string searchVal = txtSearchMenu.Text.ToLower();
    foreach (ListViewItem item in lvMenuItems.Items)
    {
        foreach (ListViewItem.ListViewSubItem subSearch in item.SubItems)
        {
            // move condition here
            if (searchVal != "" && subSearch.Text.ToLower().Contains(searchVal) == true)
            {
                subSearch.BackColor = Color.MediumAquamarine;
            }
            else
            {
                subSearch.BackColor = Color.White;
            }
        }
        item.UseItemStyleForSubItems = false;
    }
}