Please Help: Cannot get value

[Brent]

Hello,

I am new at programming. I want to email the value of the item selected in RadSlider.

The RadSlider looks like this:

 <telerik:RadSlider ID="RadSlider1" runat="server" ItemType="Item" Skin="WebBlue"
                 Width="717px" Height="66px"
             OnClientValueChange="UpdateVisibleSlide" OnClientLoaded="UpdateVisibleSlide"
              TrackPosition="TopLeft" AppendDataBoundItems="True" Length="720" >
                <Items>
             <telerik:RadSliderItem Text="Water" Height="100" Value="1"/>
             <telerik:RadSliderItem Text="Fire" Value="2" />
             <telerik:RadSliderItem Text="Rock" Value="3"/>
             <telerik:RadSliderItem Text="Sun"  Value="4"/>
             <telerik:RadSliderItem Text="Earth" Value="5"/>
             </Items>
              </telerik:RadSlider>

I read this forum and followed teh instrcutions in another post about how to get teh value, but it didn't work.

This is what I wrote:

 Dim mm As New MailMessage()
        Dim slider As RadSlider = TryCast(RadSlider1.FindControl("rslider"), Telerik.Web.UI.RadSlider)
        Dim value As Integer = slider.Value
        Dim routsegid As String = slider.Items(value).Value.ToString()
        'Assign the MailMessage's properties
        mm.Subject = "Contact Form"
       mm.IsBodyHtml = False
        mm.Body = "The following enquiry has been received from the web on " & DateTime.Now.ToString("D") & ":" & vbCrLf & vbCrLf & _
   "Product: " & (slider.Items(value).Value.ToString()) & vbCrLf & vbCrLf &

        Dim smtp As New SmtpClient

The error is saying that

Line 31:         Dim value As Integer = slider.Value

System.NullReferenceException: Object reference not set to an instance of an object.
Please help me make this work. It is probably something simple, but as I said, I am a beginner at this.

Best,

Brent.

[Svetlina Anati]

Hi Brent,

The error is due to the fact that the RadSlider control was not correctly referenced and it is null - since you do not have a RadSlider, you cannot get its value.

However, when I examined your code, I noticed that the RadSlider you have declared has ID=RadSlider1 and after that in the FindControl method you are looking for a RadSlider with ID=rslider. Please, make sure that both IDs are the same, e.g modify your code in the following manner:

Dim mm As New MailMessage()
        Dim slider As RadSlider = TryCast(RadSlider1.FindControl("RadSlider1"), Telerik.Web.UI.RadSlider)
        Dim value As Integer = slider.Value
        Dim routsegid As String = slider.Items(value).Value.ToString()
        'Assign the MailMessage's properties
        mm.Subject = "Contact Form"
       mm.IsBodyHtml = False
        mm.Body = "The following enquiry has been received from the web on " & DateTime.Now.ToString("D") & ":" & vbCrLf & vbCrLf & _
   "Product: " & (slider.Items(value).Value.ToString()) & vbCrLf & vbCrLf &

        Dim smtp As New SmtpClient

Best wishes,
Svetlina
the Telerik team

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[Brent]

Svetlina,

Thank you for your help, but I am still getting the same error after changing the code as you suggest.

The error says the line "Dim value As Integer = slider.Value" is wrong

Can you please have another look at it? Is there something else wrong? 

Best,

Brent

[Svetlina Anati]

Hi Brent,

The FindControl method is used for searching the page naming container for a server control with the specified identifier - it is useful in scenarios with INaming Containers as e.g  MasterPage and User Control. You can find more information about it below:

http://msdn.microsoft.com/en-us/library/31hxzsdw.aspx

After I again examined your code, I noticed that you have actually used this method of the RadSlider itself - since it is not a container element at all, this usage is incorrect. And since you can reference directly the slider by its ID all you should do is to get the value in the following manner:

Dim value As Integer = RadSlider1.Value

Sincerely yours,
Svetlina
the Telerik team

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[Brent]

Thank you Svetlina! Its working now.

Brent