Using the MouseMove event, you can keep track of the index of the item that the mouse is over and store this in a variable that keeps its value between MouseMoves. Every time MouseMove is triggered, it checks to see if the index has changed. If so, it disables the tooltip, changes the tooltip text for this control, then re-activates it.
Below is an example where a single property of a Car class is shown in a ListBox, but then full information is shown when hovering over any one row. To make this example work, all you need is a ListBox called lstCars with a MouseMove event and a ToolTip text component called tt1 on your WinForm.
Definition of the car class:
class Car
{
// Main properties:
public string Model { get; set; }
public string Make { get; set; }
public int InsuranceGroup { get; set; }
public string OwnerName { get; set; }
// Read only property combining all the other informaiton:
public string Info { get { return string.Format("{0} {1}\nOwner: {2}\nInsurance group: {3}", Make, Model, OwnerName, InsuranceGroup); } }
}
Form load event:
private void Form1_Load(object sender, System.EventArgs e)
{
// Set up a list of cars:
List<Car> allCars = new List<Car>();
allCars.Add(new Car { Make = "Toyota", Model = "Yaris", InsuranceGroup = 6, OwnerName = "Joe Bloggs" });
allCars.Add(new Car { Make = "Mercedes", Model = "AMG", InsuranceGroup = 50, OwnerName = "Mr Rich" });
allCars.Add(new Car { Make = "Ford", Model = "Escort", InsuranceGroup = 10, OwnerName = "Fred Normal" });
// Attach the list of cars to the ListBox:
lstCars.DataSource = allCars;
lstCars.DisplayMember = "Model";
}
The tooltip code (including creating the class level variable called hoveredIndex):
// Class variable to keep track of which row is currently selected:
int hoveredIndex = -1;
private void lstCars_MouseMove(object sender, MouseEventArgs e)
{
// See which row is currently under the mouse:
int newHoveredIndex = lstCars.IndexFromPoint(e.Location);
// If the row has changed since last moving the mouse:
if (hoveredIndex != newHoveredIndex)
{
// Change the variable for the next time we move the mouse:
hoveredIndex = newHoveredIndex;
// If over a row showing data (rather than blank space):
if (hoveredIndex > -1)
{
//Set tooltip text for the row now under the mouse:
tt1.Active = false;
tt1.SetToolTip(lstCars, ((Car)lstCars.Items[hoveredIndex]).Info);
tt1.Active = true;
}
}
}
