ImageMapEventArgs.PostBackValue Property
Gets the String assigned to the PostBackValue property of the HotSpot object that was clicked.
Assembly: System.Web (in System.Web.dll)
Property Value
Type: System.StringThe String assigned to the PostBackValue property of the HotSpot object that was clicked.
Use this property to programmatically access the PostBackValue property of the HotSpot object in an ImageMap control that was clicked.
The following code example demonstrates how to create an event handler for the Click event. The ImageMap control contains two RectangleHotSpot objects. The ImageMap.HotSpotMode property is set to HotSpotMode.PostBack, which causes the page to post back to the server each time a user clicks one of the RectangleHotSpot objects. The Click event is handled by the VoteMap_Clicked event handler. The handler examines the PostBackValue property, sent in the ImageMapEventArgs data to determine which RectangleHotSpot object is associated with the event. For this example to work correctly, you must supply your own image for the ImageUrl property and update the path to the image appropriately so that the application can locate it.
<%@ Page Language="VB" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <script runat="server"> Sub VoteMap_Clicked(ByVal sender As Object, ByVal e As ImageMapEventArgs) Dim coordinates As String Dim hotSpotType As String Dim yescount As Integer Dim nocount As Integer If (ViewState("yescount") IsNot Nothing) Then yescount = Convert.ToInt32(ViewState("yescount")) Else yescount = 0 End If If (ViewState("nocount") IsNot Nothing) Then nocount = Convert.ToInt32(ViewState("nocount")) Else nocount = 0 End If ' When a user clicks the "Yes" hot spot, ' display the hot spot's name and coordinates. If (e.PostBackValue.Contains("Yes")) Then yescount += 1 coordinates = Vote.HotSpots(0).GetCoordinates() hotSpotType = Vote.HotSpots(0).ToString() Message1.Text = "You selected " & hotSpotType & " " & e.PostBackValue & ".<br />" & _ "The coordinates are " & coordinates & ".<br />" & _ "The current vote count is " & yescount.ToString() & _ " yes votes and " & nocount.ToString() & " no votes." ' When a user clicks the "No" hot spot, ' display the hot spot's name and coordinates. ElseIf (e.PostBackValue.Contains("No")) Then nocount += 1 coordinates = Vote.HotSpots.Item(1).GetCoordinates() hotSpotType = Vote.HotSpots.Item(1).ToString() Message1.Text = "You selected " & hotSpotType & " " & e.PostBackValue & ".<br />" & _ "The coordinates are " & coordinates & ".<br />" & _ "The current vote count is " & yescount.ToString() & _ " yes votes and " & nocount.ToString() & " no votes." Else Message1.Text = "You did not click a valid hot spot region." End If ViewState("yescount") = yescount ViewState("nocount") = nocount End Sub </script> <html xmlns="http://www.w3.org/1999/xhtml" > <head id="head1" runat="server"> <title>ImageMap Class Post Back Example</title> </head> <body> <form id="form1" runat="server"> <h3>ImageMap Class Post Back Example</h3> <asp:imagemap id="Vote" imageurl="Images/VoteImage.jpg" width="400" height="200" alternatetext="Vote Yes or No" hotspotmode="PostBack" onclick="VoteMap_Clicked" runat="Server"> <asp:RectangleHotSpot top="0" left="0" bottom="200" right="200" postbackvalue="Yes" alternatetext="Vote yes"> </asp:RectangleHotSpot> <asp:RectangleHotSpot top="0" left="201" bottom="200" right="400" postbackvalue="No" alternatetext="Vote no"> </asp:RectangleHotSpot> </asp:imagemap> <br /><br /> <asp:label id="Message1" runat="Server"> </asp:label> </form> </body> </html>
Available since 2.0