Link button requires two clicks to refresh page

I have an update panel.  Inside the panel there is a gridview.  The gridview has several rows and each row has a dropdown list and a link button.  

The link button hides the current panel and shows another panel based on what the user selected in the drop down.  

I am trying to trap when the user does not select anything in the drop down list and pop an alert.  

The alert message code from the code behind:
 Protected Sub gvcadence_RowCommand(sender As Object, e As System.Web.UI.WebControls.GridViewCommandEventArgs) Handles gvcadence.RowCommand

If e.CommandName = "Change" Then
  If ddlCadence.SelectedIndex = -1 Then
    str.Append("<script type=""text/javascript"" language=""javascript"">" & vbCr)
    str.Append("" & vbCr)
    str.Append("alert(You Must Select A Cadence Name.);" & vbCr)
    str.Append("" & vbCr)
    str.Append("" & vbCr)
    str.Append("</script>" & vbCr)
    ScriptManager.RegisterClientScriptBlock(Me, Me.gvcadence.GetType(), Guid.NewGuid().ToString(), str.ToString, False)
  End if
End if         

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This what the UI looks like
 <asp:updatepanel id="upSubCategories" runat="server"  >
 <contenttemplate>
<asp:gridview id=gvcadence runat="server" AutoGenerateColumns="false" OnRowEditing="gvcadence_RowEditing" >
// other controls have been omitted
<asp:LinkButton ID="btnChangeCadence"  Text="Change"  runat="server" CommandName="Change" onClick="btnChangeCadence_Click" >
</asp:LInkButton>
</asp:gridview>
</contenttemplate>
</asp:undatepanel>

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This is the codebehind for the onClick Event
Protected Sub btnChangeCadence_Click(sender As Object, e As System.EventArgs) Handles btnChangeCadence.Click
            Me.upHeader.Visible = False
            Me.upSubCategories.Visible = False

            Me.lnkEdit.Visible = True
            Me.lnkClose.Visible = True
            BindCadenceGrid()
            Me.upChgPanel.Visible = True

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When I don't select anything from the drop down then I get an alert, but when I select something in the dropdown list, then I have to click on the button twice in order for the next panel to become visible.  

I can't figure out what is making me have to click twice.  

Can someone take a look.  Much appreciated.
sherbug1015Asked:
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CodeCruiserConnect With a Mentor Commented:
Change your rowcommand sub to following and remove the click handler of linkbutton


Protected Sub gvcadence_RowCommand(sender As Object, e As System.Web.UI.WebControls.GridViewCommandEventArgs) Handles gvcadence.RowCommand

If e.CommandName = "Change" Then
                      If ddlCadence.SelectedIndex = -1 Then
                          str.Append("<script type=""text/javascript"" language=""javascript"">" & vbCr)
                          str.Append("" & vbCr)
                          str.Append("alert(You Must Select A Cadence Name.);" & vbCr)
                          str.Append("" & vbCr)
                          str.Append("" & vbCr)
                          str.Append("</script>" & vbCr)
                          ScriptManager.RegisterClientScriptBlock(Me, Me.gvcadence.GetType(), Guid.NewGuid().ToString(), str.ToString, False)
            Else
                          Me.upHeader.Visible = False
                          Me.upSubCategories.Visible = False

                          Me.lnkEdit.Visible = True
                          Me.lnkClose.Visible = True
                          BindCadenceGrid()
                          Me.upChgPanel.Visible = True
            End if
End if         
End Sub

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0
 
Roopesh ReddyIT AnalystCommented:
Hi,

In the first place, it's better to validate DropDownList at client side than on server side -
http://roopeshreddy.wordpress.com/2012/06/09/asp-net-sever-controls-validation-using-javascript-jquery/

Hope it helps u...
0
 
Easwaran ParamasivamCommented:
0
 
Michel PlungjanIT ExpertCommented:
You do need quotes in the script but why the extreme formatting of the script?

str.Append("<script type=""text/javascript"">alert('You Must Select A Cadence Name.');</script>" & vbCr)

is a lot easier to read
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sherbug1015Author Commented:
I think this did the trick.  Thanks.
0
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