Question: Why does a button event (ie: Button1_Click) get executed on the
first click for a textbox control which has 'autopostback=f alse', but
doesn't get executed until a second click when 'autopostback=t rue'?
For example, I set up a textbox control with autopostback=fa lse, and a
command button. If I run my page (main.aspx) I can type data into the
textbox control, then click on the button. The Button1_Click event fires
immediately.
But if I just change the autopostback=tr ue for the textbox and repeat the
same events the Button1_Click event doesn't fire until the second time I
click on the button.
Why is this?
Here is my stuff:
Partial Class Main
Inherits System.Web.UI.P age
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArg s)
Handles Me.Load
If (Not IsPostBack) Then
ddAnimals.Items .Add("Mouse")
ddAnimals.Items .Add("Kangaroo" )
ddAnimals.Items .Remove("Moose" )
Else
Response.Write( "This is a Page_Load due to PostBack.")
End If
End Sub
Protected Sub ddAnimals_Selec tedIndexChanged (ByVal sender As Object, ByVal e
As System.EventArg s) Handles ddAnimals.Selec tedIndexChanged
My.Response.Wri te("Selected index changed in ddAnimals. Index value = " & _
ddAnimals.Selec tedIndex.ToStri ng & ". Data value = " & _
ddAnimals.Items (ddAnimals.Sele ctedIndex).ToSt ring & ".")
'Response.Write (Request.Form)
End Sub
Protected Sub Button1_Click(B yVal sender As Object, ByVal e As
System.EventArg s) Handles Button1.Click
Response.Write( "Button clicked")
'Response.Write (Request.Form)
End Sub
Protected Sub txtBookname_Tex tChanged(ByVal sender As Object, ByVal e As
System.EventArg s) Handles txtBookname.Tex tChanged
'Response.Write ("Text Changed in textbox! New value = " & txtBookname.Tex t)
End Sub
End Class
<%@ Page Language="VB" AutoEventWireup ="false" CodeFile="Main. aspx.vb"
Inherits="main" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dt d">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitl ed Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Text Box ID="txtBookname " runat="server"
AutoPostBack="T rue"></asp:TextBox>
<asp:RequiredFi eldValidator ID="rfvBookname " runat="server"
ControlToValida te="txtBookname "
ErrorMessage="R equired input." ToolTip="Valida tion of Book Name field"
Width="1px">*</asp:RequiredFie ldValidator>
<asp:DropDownLi st ID="ddAnimals" runat="server" AutoPostBack="F alse">
<asp:ListItem>D og</asp:ListItem>
<asp:ListItem>P ig</asp:ListItem>
<asp:ListItem>H orse</asp:ListItem>
<asp:ListItem Value="Bull">Co w</asp:ListItem>
<asp:ListItem>M oose</asp:ListItem>
</asp:DropDownLis t>
<br />
<br />
<br />
<br />
<asp:Menu ID="mnuMain" runat="server">
<Items>
<asp:MenuItem Navigateurl="se arch.aspx" target="_blank" Text="SEARCH"
ToolTip="Search contracting out notices"
Value="SEARCH"> </asp:MenuItem>
</Items>
</asp:Menu>
<br />
<br />
<asp:Validation Summary ID="vsMainPage " runat="server" Height="197px"
Width="468px" />
<asp:Button ID="Button1" runat="server" Text="Button" /></div>
</form>
</body>
</html>
