Custom Control vs User Control

S.No	Custom Control	User Control
1	A loosely coupled control w.r.t code and UI.	A tightly coupled control w.r.t code and UI.
2	Derives from Control.	Derives from UserControl.
3	Defines UI in a ResourceDictionary.	Defines UI as normal XAML.
4	UI is skinable.	Child controls are skinable.
5	Has dynamic layout.	Has static layout.
6	UI can be changed in different projects.	UI is fixed and can't have different looks in different project.
7	Has full toolbox support.	Can't be added to the toolbox.
8	Defines a single control.	Defines a set of controls.
9	More flexible.	Not very flexible like a Custom Control.

Display Cell Value into ListBox in C#.Net

Add  DataGridview,Button  and ListBox in your form.
Create  one method for getting Particular Cell data for listbox:

void DisplayCellDataintoListBox(int cellId)
{ foreach (DataGridViewRow row in dataGridView1.Rows)
{ listBox1.Items.Add(Convert.ToString(row.Cells[cellId].Value));
}
}

Call this method in the Button Click event:
DisplayCellDataintoListBox(<Pass Datagridview CellId>);