C# right. There is a MouseEnter and MouseLeave event for all the objects. Use those events and the code below.
To make it show up:
To make it fade out:
private ToolTip toolTip = new ToolTip();
string s = "ID: " + id.ToString() + "ect...";
toolTip.Show(s, this, 2000);
s << string that will be displayed
this << is the form
2000 << Duration (2seconds).
... Do you need the code to read from a text file... just google there are thousand tutorials that can explain it perfectly. If you need to get the values out of the text file show us how you have the text file set up.