get value from child from to parent form <p>i have 2 form in my media player project i have make object of from1 (parent form) and by that get value from form1 in form3. but i also need to get value of a variable from form3 to form1. but the problem is that when i make the object of form3 in form1 like this </p> <pre><code> Form3 m_child; public Form1(Form3 frm3) { InitializeComponent(); m_child = frm3; } </code></pre> <p>it shows the error in the <strong>program.cs</strong> that <strong>from1 does not contain a constructor that contain 0 argument</strong>. i know i have to pass there a parameter in <code>Application.Run(new Form1());</code> </p> <p>but what i should pass i have no idea. plz help if is there any solution or any other way to get the value from child to parent form. </p> <p>this is my code for form3 now i want to use value of smileplay, surpriseplay ,sadplay,normalplay,ambiguousplay in form1</p> <pre><code> Form1 m_parent; public Form3(Form1 frm1) { InitializeComponent(); m_parent = frm1; } private void Form3_Load(object sender, EventArgs e) { WMPLib.IWMPPlaylistArray allplaylist= m_parent.axWindowsMediaPlayer1.playlistCollection.getAll(); for (int litem = 0; litem &lt; allplaylist.count; litem++) { smilecombo.Items.Add( allplaylist.Item(litem).name); surprisecombo.Items.Add(allplaylist.Item(litem).name); sadcombo.Items.Add(allplaylist.Item(litem).name); normalcombo.Items.Add(allplaylist.Item(litem).name); ambiguouscombo.Items.Add(allplaylist.Item(litem).name); } } private void savebtn_Click(object sender, EventArgs e) { WMPLib.IWMPPlaylist smileplay= m_parent.axWindowsMediaPlayer1.playlistCollection.getByName(smilecombo.SelectedItem.ToString()).Item(0); WMPLib.IWMPPlaylist surpriseplay = m_parent.axWindowsMediaPlayer1.playlistCollection.getByName(surprisecombo.SelectedItem.ToString()).Item(0); WMPLib.IWMPPlaylist sadplay = m_parent.axWindowsMediaPlayer1.playlistCollection.getByName(sadcombo.SelectedItem.ToString()).Item(0); WMPLib.IWMPPlaylist normalplay = m_parent.axWindowsMediaPlayer1.playlistCollection.getByName(normalcombo.SelectedItem.ToString()).Item(0); WMPLib.IWMPPlaylist ambiguousplay = m_parent.axWindowsMediaPlayer1.playlistCollection.getByName(ambiguouscombo.SelectedItem.ToString()).Item(0); } </code></pre>