UserControl events

CalA · Apr 28, 2012

Hi, I was wondering if it is possible to add an event to a UserControl. Specifically, if there is a DropDownList in a UserControl, can the main aspx page holding this UserControl respond to the OnSelectedIndexChanged event of the DropDownList? Are there any articles about this? I have read about accessing the properties and methods of UserControls, but seen nothing about UserControl events. Thanks, JON Within the Page_Load of the UserControl add the following line where "ctlName" is the name of your UserControl: AddHandler ctlName.SelectedIndexChanged, New System.EventHandler(AddressOf Control_ChangeEvent) Then, add a method to handle the event in the UserControl: Public Sub Control_ChangeEvent(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ctlName.SelectedIndexChanged      RaiseEvent OnSelectedIndexChange(Me, e) End Sub In your ASPX file, register the UserControl as normal, and add the event handler: OnSelectedIndexChanged="SomeMethod" Then in your code-behind, just add a method to handle the event: Sub SomeMethod(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ctlName.OnSelectedIndexChange      ' --- Some Code Here End Sub That's it! Hope this helps... Jason Hi Jason, I tried out your code, but got the following error: "Handles clause requires a WithEvents variable" pointing to this line as the culprit: "Public Sub Control_ChangeEvent(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ddDropDown.SelectedIndexChanged" Also, just wanted to check I'd understood you correctly. Where you say "...where "ctlName" is the name of your UserControl...", I assume you mean the id of the DropDownList within the UserControl - correct? Thanks for your help so far, JON Jon, Yep, "ctlName" should be the id of the DropDownList within the UserControl. In the code-behind, when you declare your WebControl that inherits from the UserControl, you should declare it as follows: Protected WithEvents ddDropDown As ClassName Basically the "WithEvents" just allows the WebControl to handle events such as SelectedIndexChanged. Also make sure that you declare it as the ClassName contained in your UserControl code. Good luck! JasonHi Jason, Aaaargh! Getting confused! This is new stuff for me, and I'm not really getting very far... The latest error message is: 'OnSelectedIndexChange' is not an event of 'ASP.Maz' Pointing to the line in the .ascx file: RaiseEvent OnSelectedIndexChange(Me, e) Here's the code I'm working on - any chance you can just lead me through the lines I have to change? Thanks for the help! JON ++++++++++++++++++++++++++++++++++++++++ JasonMurphy_Code.aspx - the parent page ++++++++++++++++++++++++++++++++++++++++ <%@ Page Language="VB" Trace="false" Debug="true" %> <%@ Register TagPrefix="UserControl" TagName="ExampleUserControl" src=http://aspmessageboard.com/archive/index.php/"JasonMurphy_Code.ascx" %> <script language="VB" runat="server"> Sub Page_Load(sender as object, e as eventargs) 'sth here End Sub Sub ExampleMethod(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles UserControl1.OnSelectedIndexChange ' --- Some Code Here End Sub </script> <html> <body> <form runat="server" name="form1" id="form1"> <UserControl:ExampleUserControl id="UserControl1" runat="server" OnSelectedIndexChanged="ExampleMethod" /> </form> </body> </html> ++++++++++++++++++++++++++++++++++++++++++++++ JasonMurphy_Code.ascx - the User Control page ++++++++++++++++++++++++++++++++++++++++++++++ <%@ Control Language="VB" ClassName="Maz" %> <script language="VB" runat="server"> Sub Page_Load(obj as object, e as EventArgs) Dim myAL1 As New ArrayList() myAL1.Add("DDL1FirstItem") myAL1.Add("DDL1SecondItem") myAL1.Add("DDL1ThirdItem") DDL1.DataSource = myAL1 DDL1.DataBind() Dim myAL2 As New ArrayList() myAL2.Add("DDL2FirstItem") myAL2.Add("DDL2SecondItem") myAL2.Add("DDL2ThirdItem") DDL2.DataSource = myAL2 DDL2.DataBind() AddHandler DDL1.SelectedIndexChanged, New System.EventHandler(AddressOf Control_ChangeEvent1) AddHandler DDL2.SelectedIndexChanged, New System.EventHandler(AddressOf Control_ChangeEvent2) end sub Protected WithEvents DDL1 As DropDownList Public Sub Control_ChangeEvent1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DDL1.SelectedIndexChanged RaiseEvent OnSelectedIndexChange(Me, e) End Sub Protected WithEvents DDL2 As DropDownList Public Sub Control_ChangeEvent2(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DDL2.SelectedIndexChanged RaiseEvent OnSelectedIndexChange(Me, e) End Sub </script> <html> <body> <form runat="server"> First DropDown: <asp

ropDownList id="DDL1" runat="server" AutoPostBack="true" /> <hr> Second Drop Down: <asp

ropDownList id="DDL2" runat="server" AutoPostBack="true" /> </form> </body> </html>Oops! There's a VERY important line that I forgot to include in the code. Within the code for your UserControl add: Public Event OnSelectedIndexChange(ByVal Sender As System.Object, ByVal e As System.EventArgs) That should be the only remaining line. Hopefully I didn't overlook any additional ones, but I don't think I did! JasonHi James, Hope you're still with me! Progress is being made, one step at a time.... Have added the line: Public Event OnSelectedIndexChange(ByVal Sender As System.Object, ByVal e As System.EventArgs) to the ascx file as suggested, am now getting error: 'DDL1' is already declared as 'Protected Dim WithEvents DDL1 As System.Web.UI.WebControls.DropDownList' in this class. pointing to this line as culprit: <asp

ropDownList id="DDL1" runat="server" AutoPostBack="true" /> Full code for ascx file below - grateful, as ever, for your help! Cheers, JON ************************************************* <%@ Control Language="VB" ClassName="Maz" %> <script language="VB" runat="server"> Sub Page_Load(obj as object, e as EventArgs) Dim myAL1 As New ArrayList() myAL1.Add("DDL1FirstItem") myAL1.Add("DDL1SecondItem") myAL1.Add("DDL1ThirdItem") DDL1.DataSource = myAL1 DDL1.DataBind() Dim myAL2 As New ArrayList() myAL2.Add("DDL2FirstItem") myAL2.Add("DDL2SecondItem") myAL2.Add("DDL2ThirdItem") DDL2.DataSource = myAL2 DDL2.DataBind() AddHandler DDL1.SelectedIndexChanged, New System.EventHandler(AddressOf Control_ChangeEvent1) AddHandler DDL2.SelectedIndexChanged, New System.EventHandler(AddressOf Control_ChangeEvent2) end sub Public Event OnSelectedIndexChange(ByVal Sender As System.Object, ByVal e As System.EventArgs) Protected WithEvents DDL1 As DropDownList Public Sub Control_ChangeEvent1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DDL1.SelectedIndexChanged RaiseEvent OnSelectedIndexChange(Me, e) End Sub Protected WithEvents DDL2 As DropDownList Public Sub Control_ChangeEvent2(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DDL2.SelectedIndexChanged RaiseEvent OnSelectedIndexChange(Me, e) End Sub </script> <html> <body> <form runat="server"> First DropDown: <asp

ropDownList id="DDL1" runat="server" AutoPostBack="true" /> <hr> Second Drop Down: <asp

ropDownList id="DDL2" runat="server" AutoPostBack="true" /> </form> </body> </html>

UserControl events

CalA

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