NullReferenceException Error - Wizard Template

[Morris Neuman]

Hi,
I have a web page with a master page and a contents page. On the contents
page I have a wizard as defined below:
<asp:Wizard ID="Wizard1" runat="server" ActiveStepIndex="1"
DisplayCancelButton="True" Height="85px" Width="647px"
OnNextButtonClick="NextButtonClick_SkipStep"
OnActiveStepChanged="OnActiveStepChanged_SaveCurrPrevIndex"

CancelDestinationPageUrl="~/SystemAdminOnly/CMTables/OutcallSchedule/ManageOutcallSchedule-LoadNumbers.aspx"
DisplaySideBar="False">
<StepStyle HorizontalAlign="Left" VerticalAlign="Top" />
<StartNavigationTemplate>
<asp:Button ID="StartNextButton" runat="server"
CommandName="MoveNext" Visible="false"
Text="Next" />
<asp:Button ID="CancelButton" runat="server"
CausesValidation="False"
CommandName="Cancel" Text="Cancel" />
</StartNavigationTemplate>
<WizardSteps>
<asp:WizardStep runat="server" StepType="Start" title="Step 1">
<code style="font-family: Verdana; font-size: 10pt; color:
navy; ">Step1...</code>
</asp:WizardStep>
<asp:WizardStep runat="server" StepType="Start" title="Step 2">
<code style="font-family: Verdana; font-size: 10pt; color: navy;
">Step2...</code>
</asp:WizardStep>
</asp:WizardSteps>
<SideBarStyle VerticalAlign="Top" />
<StepNavigationTemplate>
<asp:Button ID="StepPreviousButton" runat="server"
CausesValidation="False"
CommandName="MovePrevious" Text="Previous" />
<asp:Button ID="StepNextButton" runat="server"
CommandName="MoveNext"
Text="Next" Visible="false"/>
<asp:Button ID="CancelButton" runat="server"
CausesValidation="False"
CommandName="Cancel" Text="Cancel" />
</StepNavigationTemplate>
</asp:Wizard>

I also have a script defined to set display of the StepNextButton in the
StepNavigationTemplate.
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
TextBox3.Text = "0";
TextBox4.Text = "0";
}
}

protected void OnActiveStepChanged_SaveCurrPrevIndex(object sender,
EventArgs e)
{
if (IsPostBack)
//NOT first time
{
TextBox3.Text = TextBox4.Text;
TextBox4.Text = Wizard1.ActiveStepIndex.ToString();
}

if (Wizard1.ActiveStepIndex == 1)
{
Button btn =
(Button)Wizard1.FindControl("StepNavigationTemplateContainerID$StepNextButton");
btn.Visible = true;
}

if (Wizard1.ActiveStepIndex >1)
{
Button btn =
(Button)Wizard1.FindControl("StepNavigationTemplateContainerID$StepNextButton");
btn.Visible = false;
}
}

When this page is activated, I get the following error:
Exception Details: System.NullReferenceException: Object reference not set
to an instance of an object.

Source Error:
Line 53: {
Line 54: Button btn =
(Button)Wizard1.FindControl("StepNavigationTemplateContainerID$StepNextButton");
Line 55: btn.Visible = true;
Line 56: }
Line 57:

Can you tell me why and what I need to change?

 

[Thomas Sun [MSFT]]

Hi Morris,

Based on the code you posted, you set Wizard's ActiveStepIndex to "1" When
we request the page first time, and the control has not been initialized in
OnActiveStepChanged event, so we receive the exception.

In this case, you can find control and set its property in PageLoad event
when page is requested first time.
=================================================
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
TextBox3.Text = "0";
TextBox4.Text = "0";

//
//TO DO: Find Control and set its property when page is
requested first time
//

}

}

protected void OnActiveStepChanged_SaveCurrPrevIndex(object sender,
EventArgs e)
{
if (IsPostBack)
//NOT first time
{
TextBox3.Text = TextBox4.Text;
TextBox4.Text = Wizard1.ActiveStepIndex.ToString();

//
//TO DO: Find Control and set its property when page is NOT
requested first time.
//
if (Wizard1.ActiveStepIndex == 1)
{
Button btn =

(Button)Wizard1.FindControl("StepNavigationTemplateContainerID$StepNextButto
n");
btn.Visible = true;
}

if (Wizard1.ActiveStepIndex > 1)
{
Button btn =

(Button)Wizard1.FindControl("StepNavigationTemplateContainerID$StepNextButto
n");
btn.Visible = false;
}

}
}

=================================================

I look forward to receiving your test results.


--

Best Regards,
Thomas Sun

Microsoft Online Partner Support

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[Morris Neuman]

It worked.