Hello all. I am trying to implement my first server control and have
run into two problems that I cannot solve. I need the assistance of
someone with more experience.
My goal was to create an input button that would allow for both text
and an image on it. I am attempting to accomplish this by basing off
of the asp:button control. I added a property for the image url and
one to determine if the image is displayed on the left or right of the
text. I am also overriding the necessary methods so that the html that
is rendered is correct. (The code is included below.)
In my aspx file I put two instances of the control:
<tlic:ImageTextButton ID="btnSaveAll" runat="server" Text="Save All"
ImageUrl="Images/Diskette.gif" />
<tlic:ImageTextButton ID="btnEmailAll" runat="server" Text="Email All"
ImageUrl="Images/Envelope.gif" OnClientClick="return GetRecipients();"
/>
It renders the following in the html to the browser:
<button type="submit" name="btnSaveAll" value="Save All"
id="btnSaveAll"><img id="btnSaveAll_Img" name="btnSaveAll:Img"
src="Images/Diskette.gif" border="0" /> Save All</button>
<button type="submit" name="btnEmailAll" value="Email All"
onclick="return GetRecipients();" language="javascript"
id="btnEmailAll"><img id="btnEmailAll_Img" name="btnEmailAll:Img"
src="Images/Envelope.gif" border="0" /> Email All</button>
So far, all is good. The problems come in when I click one of the
buttons. The first problem is that ASP.NET complains when validating
the response because the value of the button is being returned as the
inner html rather than what is in the Value attribute. Since there is
an IMG tag there it thinks the data is suspect. Here is the form data:
__EVENTTARGET
__EVENTARGUMENT
__VIEWSTATE /wEPDwUKMTgzNj(snip)...
emailRecipients
gridAuthKeys:_ctl2:tbRANumber
gridAuthKeys:_ctl2:tbPONumber
gridAuthKeys:_ctl2:tbMustArriveBy
btnSaveAll <IMG id=btnSaveAll_Img src="Images/Diskette.gif" border=0
name=btnSaveAll:Img> Save All
btnEmailAll <IMG id=btnEmailAll_Img src="Images/Envelope.gif" border=0
name=btnEmailAll:Img> Email All
I figured I would deal with that later so I turned off page validation
to see if the rest of the processing would work. The second problem is
that no matter which button I click, ASP.NET fires off the event
handler for which ever is the last, or second, button, in this case
"email all". Again, I think the value of the button controls is
messing it up.
I tried setting the buttons to UseSubmit=False vs. True but that
didn't help. An interesting thing to note is that according to the
HTML spec, if a form contains more than one submit button, only the one
clicked is supposed to be included in the form data returned. This is
not what is happening here.
I would greatly appreciate any time that someone could spend to help me
with this.
Regards,
David
Here is the code for the control:
Imports Microsoft.VisualBasic
Imports System
Imports System.Web
Imports System.Web.UI
Imports System.ComponentModel
Imports System.Drawing.Design
Namespace TLI.Controls
''' <summary>
''' A control rendered as a button that has both an image and text.
''' </summary>
''' <remarks></remarks>
<ToolboxData("<{0}:ImageTextButton
runat=server></{0}:ImageTextButton>")_
Public Class ImageTextButton
Inherits WebControls.Button
<Bindable(True), _
Category("Appearance"), _
DefaultValue(""), _
Editor("System.Windows.Forms.ImageEditorIndex, System.Design",
GetType(UITypeEditor)), _
Description("The image to appear on the button")_
Public Property ImageUrl() As String
Get
Dim s As String = CStr(ViewState("ImageURL"))
Return IIf(s Is Nothing, "", s)
End Get
Set(ByVal value As String)
ViewState("ImageURL") = value
End Set
End Property
<Bindable(True), _
Category("Appearance"), _
DefaultValue(True), _
Description("True if the image is to appear to the left of the
text")_
Public Property ImageLeft() As Boolean
Get
Dim o As Object = ViewState("ImageLeft")
Return IIf(o Is Nothing, True, CBool(o))
End Get
Set(ByVal value As Boolean)
ViewState("ImageLeft") = value
End Set
End Property
Protected Overrides ReadOnly Property TagKey() As
HtmlTextWriterTag
Get
Return HtmlTextWriterTag.Button
End Get
End Property
Protected Overrides Sub RenderContents(ByVal writer As
System.Web.UI.HtmlTextWriter)
If ImageLeft Then
RenderImage(writer)
writer.Write(" ")
End If
writer.Write(Text)
If Not ImageLeft Then
writer.Write(" ")
RenderImage(writer)
End If
End Sub
Private Sub RenderImage(ByVal writer As
System.Web.UI.HtmlTextWriter)
writer.AddAttribute(HtmlTextWriterAttribute.Id, ID &
"_Img")
writer.AddAttribute(HtmlTextWriterAttribute.Name, ID &
":Img")
writer.AddAttribute(HtmlTextWriterAttribute.Src, ImageUrl)
writer.AddAttribute(HtmlTextWriterAttribute.Border , "0")
writer.RenderBeginTag(HtmlTextWriterTag.Img)
writer.RenderEndTag()
End Sub
End Class
End Namespace
