Server Error in ‘/’ Application.

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 – Error Locating Server/Instance Specified)

I recently migrated my dedicated server from the worthless company AIT to the cloud computing division of RackSpace. As a result I had to move my SQL database. No Problem I thought. I’ll just edit my web.config and go about my merry business. Well that is when the above error appeared.  This peticular site is dynamically compiled VB site with code in the aspx pages. (no code behind).

The data access layer is handled by some dataset files with XSD extentions. I found that when the files were created the web config connections strings were coppied but not dynamically linked. Each table adpter’s connection sting needed pointed at the web config again. The process was slow due to the now-remote database.

Now that the table adapters have updated their connection strings all is well.

The application I’m working on has a list of email addresses for each contact. Rather than creating a new table with forgein keys, stored procedures, Data access componants, and business layer logic I decided to take a regular email field and expand it to store a list of emails. My Datastore is SQL Server. I only changed the field to nvarchar(max).

To save the list

1. edit the list as needed
2. pull the listbox.items collection and convert to an array
3. Serialize the array and store the text in the database

To get it back

1. read the text from the database
2. de-serialize to an array
3. load the array as items in the listbox

The issue I had was that the xmlserializer works with streams. This I was not used to. I needed to convert from string to stream and backagain. Looking back it isn’t hard but for me it was a learning curve.

Here is the code then pulls the listbox and converts the items to an XML string:

        'create and populate an array, the items collection is not serializable
         Dim emails As New ArrayList()

For Each itm As ListItem In ListBox1.Items
emails.Add(itm.Value)
Next

‘create an XmlSerializer and use it to populate a memory stream
Dim xs As New System.Xml.Serialization.XmlSerializer(GetType(ArrayList))
Dim ms As New System.IO.MemoryStream
Try
xs.Serialize(ms, emails)
Catch ex As Exception
End Try

‘rewind the stream
ms.Seek(0, 0)

‘read the stream to string, I use a StreamReader to take advantage of ReadToEnd
Dim sr As New System.IO.StreamReader(ms)
Dim str As String = sr.ReadToEnd

‘now we can save the string to a database

Here is the code that re-populates the list from an XML string

‘we’ll start with a string of xml called str. I’ll assume it’s already pulled from the database

       'To convert a string to a stream  we have to convert to a byte array first.
       'aStr is str converted to an array of bytes
        Dim uniEncoding As New UnicodeEncoding()
        Dim aStr As Byte() = uniEncoding.GetBytes(str)

      'wrtie the byte array to a stream and rewind it

        Dim ms As New System.IO.MemoryStream
        ms.Write(aStr, 0, aStr.Length)
        ms.Seek(0, 0)

      'de-serialize from xml to an array of strings
        Dim emails As New ArrayList()
        Dim xs As New System.Xml.Serialization.XmlSerializer(GetType(ArrayList))

        Try
            emails = xs.Deserialize(ms)
        Catch ex As Exception
        End Try

      'load the array into the listbox's items collection
        ListBox1.Items.Clear()
        For Each itm As Object In emails
            ListBox1.Items.Add(itm.ToString)
        Next

The jist is this: the formview was trying to use an empty string for an int field instead of Nothing.
Here is the error I saw, helpful huh?

Failed to set one or more properties on type xxxxxxx  Ensure that the input values are valid and can be converted to the corresponding property types.

The fields are allowed to be null but the formview just isn’t smart enough to use nothing instead of “”.

My workaround was simple and flexible enough to be re-used so I figured I would post it here.
I simply hijack the formview’s onInserting and replaced “” with Nothing for each field.

Protected Sub formView1_ItemInserting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.FormViewInsertEventArgs)

For Each o As DictionaryEntry In e.Values
If o.Value = “” Then e.Values(o.Key) = Nothing
Next

End Sub

This same snipit can be put on any page as is and forces certain pages to be https. The nice thing about it is that the user can not edit the url back to http on a page that has this. All I did was put it on the login page and payment page.

On page load the server examines the Request.IsSecureConnection flag and redirects if not secure. It’s that simple. To make it a re-useble snipit I get the page name dynamically.

Be sure not to include the slash after your top level domain.

If Not Page.IsPostBack Then

If Not Request.IsSecureConnection Then

Response.Redirect(“https://www.yourhostname.com” & Request.Url.PathAndQuery.ToString)

End If

End If

I did some research and found a few good examples of how to handle the errors but most were in C# and some didn’t work in Firefox. Imagine that!

Being a VB guy I decided to post a very stipped down sample of how it works.

The lowdown: The script manager is wired to an event handler that passes the exeption info to the client side java script.  Then we put some client side java script in to display the message.

<%@ Page Language="VB" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">

    Protected Sub SuccessProcessClick_Handler(ByVal sender As Object, ByVal e As System.EventArgs)
        'a successful click
        UpdatePanelMessage.Text = "The asynchronous postback completed successfully."

    End Sub

    Protected Sub ScriptManager1_AsyncPostBackError(ByVal sender As Object, ByVal e As System.Web.UI.AsyncPostBackErrorEventArgs)

        'this creates an exception in the client side Javascript. the exeption will be handled on the client side.
        ScriptManager1.AsyncPostBackErrorMessage = e.Exception.Message

    End Sub

    Protected Sub ErrorProcessClick_Handler(ByVal sender As Object, ByVal e As System.EventArgs)

        'cause an error on this click
        Dim x As Integer = 0
        Dim y As Integer = 10 / x

    End Sub
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Untitled Page</title>
      <style type="text/css">
   #AlertDiv{
     position:relative;
     visibility: hidden;
     background-color:maroon;
     color:White;
     width:500px;

    }

    </style>
</head>
<body >
    <form id="form1" runat="server">
        <div>
            <asp:ScriptManager ID="ScriptManager1" runat="server"
                onasyncpostbackerror="ScriptManager1_AsyncPostBackError" />

            <script type="text/javascript" language="javascript">
               // this is the client side script that will handle the error passed from the server.
                var divElem = 'AlertDiv';
                var messageElem = 'AlertMessage';
                var bodyTag = 'bodytag';
                Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);

               //hide or show the error div
                function ToggleAlertDiv(visString)
                {

                     var adiv = $get(divElem);
                     adiv.style.visibility = visString;

                }

                //reset the error div
                function ClearErrorState() {
                     $get(messageElem).innerHTML = '';
                     ToggleAlertDiv('hidden');                     
                }
                //put the error text into the div
                function EndRequestHandler(sender, args)
                {
                   if (args.get_error() != undefined)
                   {
                       var errorMessage = args.get_error().message;
                       args.set_errorHandled(true);
                      ToggleAlertDiv('visible');
                      //errorMessage.split(":",2)[1] = get just the message and chop off the identifier before the :
                      //The message iteself is the only usefull part to the end user.
                      $get(messageElem).innerHTML ='Error:' + errorMessage.split(":",2)[1];

                   }
                }
            </script>
            <asp:UpdatePanel runat="Server" ID="UpdatePanel1">
                <ContentTemplate>

                  <div id="AlertDiv">

                      <div id="AlertMessage"></div>

                         <input id="OKButton" type="button" value="OK" runat="server" onclick="ClearErrorState()" />

                  </div>

                        <asp:Label ID="UpdatePanelMessage" runat="server" /><br />

                        <asp:Button runat="server" ID="Button1" Text="Submit Successful Async Postback"
                            OnClick="SuccessProcessClick_Handler" OnClientClick="ClearErrorState()" />
                        <asp:Button runat="server" ID="Button2" Text="Submit Async Postback With Error"
                            OnClick="ErrorProcessClick_Handler" OnClientClick="ClearErrorState()" />

                </ContentTemplate>
            </asp:UpdatePanel>

     </div>
    </form>
</body>
</html>

At first I figured I could use a div and simply tap in to the inner html. No luck! It’s not available on the server side. I’d like to avoid the help of Javascript so I kept looking.

I decided to make my own copy of text that is generated when the grid is databound. Every time a row is databound I append the info to my string. This turned out to be pretty flexible. I can pretty much turn the data into anything I want. csv, or a html table. At first I tried plain text with tabs in between. I decided to use an html table as it ended up looking the best.

In the grid’s row databound event I add <table> if the row is a header row. I close it with </table> if the row is the footer. For everyting in between I create a <tr> then for each control with <td>

I saved this text in a hidden label that I can call later to be used in the body of an email.

Here is the source code. I use linq to poulate the gridview but you can bind the gridview to any datasource.

<%@ Page Language=”VB” %>
<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd”>
<script runat=”server”>

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)

If Not Page.IsPostBack Then

‘make some data with Linq

Dim myList() = {New With {.Name = “Bill”, .Title = “Developer”, .Age = “21″, .Birthday = “9/30″}, _
New With {.Name = “Joe”, .Title = “Tester”, .Age = “23″, .Birthday = “1/3″}, _
New With {.Name = “Tom”, .Title = “Senior Developer”, .Age = “25″, .Birthday = “3/20″}, _
New With {.Name = “Mark”, .Title = “Technician”, .Age = “41″, .Birthday = “6/26″} _

}

Me.GridView1.DataSource = myList
Me.GridView1.DataBind()

End If

End Sub

Protected Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs)

If e.Row.RowType = DataControlRowType.Header Then
Label1.Text &= vbCrLf & “<table border=’0′cellpadding=’5′ cellspacing=’5′>” & vbCrLf
End If

If e.Row.RowType <> DataControlRowType.Footer Then
Label1.Text &= vbTab & “<tr>” & vbCrLf

For Each item In e.Row.Controls

If item.visible = True Then

Label1.Text &= vbTab & vbTab & “<td>”

Label1.Text &= item.text

Label1.Text &= “</td>” & vbCrLf

End If

Next

Label1.Text &= vbTab & “</tr>” & vbCrLf

End If

If e.Row.RowType = DataControlRowType.Footer Then
Label1.Text &= “</table>” & vbCrLf
End If

End Sub

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)

Me.Label2.Text = Server.HtmlEncode(Label1.Text)

Me.Label1.Visible = True

‘ Dim msg As New System.Net.Mail.MailMessage(TO@EMAIL.COM, FROM@EMAIL.COM)

‘ msg.Subject = “Gridview email”

‘ msg.IsBodyHtml = True

‘ msg.Body = Me.Label1.Text

‘Dim smtp As New System.Net.Mail.SmtpClient

‘ smtp.Send(msg)

End Sub

</script>

<html xmlns=”http://www.w3.org/1999/xhtml”>

<head runat=”server”>

<title>Untitled Page</title>

</head>

<body>

<form id=”form1″ runat=”server”>

<div id=”div1″ runat=”server”>

<asp:GridView ID=”GridView1″ runat=”server” onrowdatabound=”GridView1_RowDataBound” AutoGenerateColumns=”False” >

<Columns>

<asp:BoundField DataField=”name” HeaderText=”Name” />
<asp:BoundField DataField=”age” HeaderText=”Age” />
<asp:BoundField DataField=”title” HeaderText=”Title” />
<asp:BoundField DataField=”birthday” HeaderText=”Birthday” />

</Columns>

</asp:GridView>

<asp:Button ID=”Button1″ runat=”server” Text=”capture this ^” onclick=”Button1_Click” />

<br />

<asp:Label ID=”Label1″ runat=”server” Visible=”False”></asp:Label>

<pre>

<asp:Label ID=”Label2″ runat=”server” Visible=”true”></asp:Label>

</pre>

</div>

</form>

</body>

</html>

The msdn documentation was a little hazy on this subject. Here it is as I understand it….

Lets start from the beginning; and adrotator will take a list of images and rotate through them every time the page loads. Some ads may need to appear more often than others. That is where the Impressions property comes in. It allows to give some ads more weight than others. Perhaps one person is paying more for the ad.

OK, so how do we use it? if every image should be weighted equally just set it to 1. Other wise you need to figure out the ratio. To figure it out you add up all the impression values in the file. Each ads ratio is it’s impression value divided by the total.

So if there were three ads in the file and they looked like this:

ad 1 imressions = 1
ad 2 impressions=2
ad 2 impressions =2

The total is 5. Ad 1 will be show 1 out of 5 times. Ad 2 will be shown 2 out of 5 times and so on.

I like to work in percentages. To do this just divy up the ads until we get to 100%.

Ad 1 impressions = 20%
Ad 2 impressions= 40%
ad 3 impressions= 40%

Just make sure they all ad up to 100 and your done.  The percentage is the number of impressions.  1, 2,2 is actually the same as 20, 40, 40 so why not base it on 100 so it’s easier to figure out?

Good Luck.

P.S. I saw a blog somewhere that wrapped an adrotator in a UpdatePanel that pdated on a timer. Interesting. Quicker than flash and more flexible than an animated gif. I’ll be filing that in the back of my mind.