I've been getting this error intermittently for a while now and finally got tired of seeing it, so I started looking for causes and solutions. The exact error I was getting is shown below. Note that it could appear with the same error 'BC30560', but have a different class name and different namespace.

Compiler Error Message: BC30560: 'Login_ascx' is ambiguous in the namespace 'ASP'

I couldn't really find a clear answer as it seems it can be caused by different scenarios, some of which may be a result of a bug in the framework. In my case it was a simple fix, although I don't know why this fixed it.

I had a page named Login.aspx and a User Control that resided on that page named Login.ascx. Why did I do it this way? Because I used the Login.aspx page as the primary login page, but there were other scenarios where I wanted to show a login without redirecting to the login page. So I created a User Control that I could put anywhere I wanted.

It seems as though there is a bug in the asp.net framework since my page and my control have different file extensions and different class names. Yet as soon as I changed my User Control to be named LoginCtrl.ascx, the error stopped appearing.

While writing a visitor tracking system for site traffic statistics, I came across this useful bit of code for resolving an IP address to a domain name. System.Net.Dns.GetHostEntry("000.000.000.000").HostName will return the domain associated with the IP passed in.

There is plenty of information out there on this error. It could occur for different reasons I suppose. My scenario was this.

I had SQL Server 2005 Express installed. I needed to install SQL Server 2005 Standard Edition. I installed Standard edition, but for some reason none of the tools were showing up. So I uninstalled both SQL Server 2005 editions and then reinstalled both, installing Standard edition first. I then tried to run my Personal Site Kit project, which uses SQL Express. That's when I received the error. Failed to generate a user instance of SQL Server due to a failure in starting the process for the user instance. The connection will be closed.

The first solution I came across seems to be the common solution for this issue. This is what worked for me.

1. Delete the directory c:\Documents and Settings\username\Local Settings\Application Data\Microsoft\Microsoft SQL Server Data\SQLEXPRESS
2. Then reboot your computer. That's it.
   

You might receive this error if your allowing users to enter text into a textbox, then saving the text to the database, and trying to display it on a page. This error might occur if characters or text deemed unsafe by the asp.net request validation feature, are entered by the user. You can easily solve this issue by html encoding input from the user.

So in your code, you would do something like this before saving the text to the database.

Dim strText As String = Server.HtmlEncode(MyTextBox.Text.Trim)
SaveToDB(strText)

When you want to display the saved text on a web page you would use something like the following.

Dim strText as String = Some code to retrieve the text from the database
MyLabel.Text = Server.HtmlDecode(strText)

This short blog post is meant to be a quick read for this issue. You can read a great article on this subject at http://www.asp.net/faq/requestvalidation.aspx

Recently I wrote about session timeout and forms authentication timeout issues. They’re really pretty straight forward when it comes to configuring them. However, problems arise when we attempt to set the forms authentication timeout to a long period of time so that users don’t have to log in every time they return to our site. In this case we tend to run into issues with users being logged in even after their session has expired.

It would be much simpler if we just set the forms authentication timeout to a time that was less than the session timeout. In this case, if the user was inactive for too long, they would be redirected to the log in page. Upon redirection to the login page you could clean up and end their session. However, if we want to allow the user to be automatically logged in on return visits, this isn’t a very good solution. In addition there are other unpleasant scenarios that can occur in this model. Take for instance the following example.

You have a user that logs into your web application and goes into edit mode on one of your webforms. When the user enters edit mode, you store a business class object in a session variable for use while they’re working with that form. The user then gets a phone call and begins a lengthy conversation about selling their house or something. While they are on the phone, the forms authentication ticket expires. The user gets off the phone and enters data into more of the fields on form and then hits save. Boom, the user gets redirected to the login page because their authentication ticket expired. They loose the data they had finished entering and aren’t very happy about it.

The solution I implemented to handle these scenarios more gracefully, is to automatically end the users session, log them out and send them to the login page when their session is about to expire.

This solution is specific to the use of a master page throughout your application. If you’re not using a master page, it would be possible to create a user control that you drop on every page to implement the same functionality. However, why not just use a master page.

In my Default.master.vb I have the following two variables declared at a module level.

Protected mintTimeout As Integer
Protected mstrLoginURL As String

Then in the Page_Init of the Default.master.vb I set the two variables.

Dim intRedirectTime As Integer = 2
mintTimeout = (Session.Timeout - intRedirectTime) * 60000
mstrLoginURL = ResolveUrl("~/endsession.aspx")

The variable intRedirectTime represents how many minutes prior to the session timeout that I want to force the redirect to the login page.

60000 represents 1minute in milliseconds. I’ll be using the window.setTimeout method so I need time in milliseconds. Every time there is a postback in the application the above code is run and sets the timeout variable to 2 minutes less than the session timeout setting. I also set the mstrLoginURL with a resolved URL for my endsession.aspx page.

Then on the Default.master just before the end body tag </body>, I put the following JavaScript section.

<script language="javascript">
 window.setTimeout("endSession();",<%=mintTimeout%>);
 function endSession()
 {
  alert("Your session has expired. You will be redirected to the login page.");
  url = '<%=mstrLoginURL %>';
  document.location=url;
 }
</script>

In the above javascript section the setTimeout method fires 2 minutes before the session is about to end. The endSession function is called which pops up an alert to notify the user that their session has ended. At this point the session is still active, but will be ended regardless once the Ok button is clicked on the alert dialog. In addition the user will be logged out using the FormsAuthentication.SignOut() method.

The page that the user is actually sent to is a blank page with the following code in the Page_Load. I have named the page endsession.aspx.

If User.Identity.IsAuthenticated = True Then
 FormsAuthentication.SignOut()
End If
Session.Abandon()
Response.Redirect("~/Login.aspx")

In the above code I check to see if the user is authenticated before trying to sign them out. I then call the Session.Abandon method and redirect them to the login page.

The solution shows what is possible with a little creativity for handling timeout issues in ASP.NET 2.0 web applications. Every application is different and may require unique solutions for handling issues that arise from the new security model in ASP.NET 2.0. I hope this article inspires ideas for others to solve the session issues they may face.

If you have any thoughts, ideas, or input on this subject, please tell me about it by leaving a comment.

When developing web applications there are often times when I need to dynamically set or change properties of controls in a page. This is a concept that is probably not implemented as much as it should be. In fact, you can create procedures that will dynamically handle controls on any page.

You can download a working sample project here.

The example I’m going to use involves dynamically adding RequiredFieldValidator controls to the page for textbox fields that are required. In this scenario I need the textbox controls inside table cell <asp:TableCell ID="formCell" runat="server">. I also need the ValidationGroup property set on each textbox to ValidationGroup="Required". I’ll use this later so I know which textbox fields are required. There are of course better ways to do this using custom business objects, but I’ll do it this way to keep it simple.

I have the following html inside the form tag on a simple default.aspx page. Below my fields I have placed a ValidationSummary.

<asp:Table ID="Table1" runat="server">
 <asp:TableRow>
  <asp:TableCell ID="formCell" runat="server">
   <table cellpadding="3" cellspacing="0" border="0">
    <tr>
     <td align="right">Name: </td>
     <td>
      <asp:TextBox ID="Name" runat="server"
       ValidationGroup="Required"/></td>
    </tr>
    <tr>
     <td align="right">Company: </td>
     <td valign="top">
      <asp:TextBox ID="Company" runat="server"/></td>
    </tr>
    <tr>
     <td colspan="2">
      <asp:Button ID="btnSubmit"
       runat="server" Text="Submit" /></td>
    </tr>
   </table>
  </asp:TableCell>
 </asp:TableRow>
</asp:Table>
<asp:ValidationSummary id="ValidationSummary1"
 DisplayMode="BulletList"
 ShowSummary="true"
 HeaderText="Please check the following fields:"
 runat="server" />

Now I want to be able to dynamically add RequiredFieldValidators for controls that are in the Required ValidationGroup. In order to do this I’m going to create a public sub named SetValidators and pass in to it the table cell that all my controls reside in as well as the Form on the page.

I’ll use a reference to the table cell to loop through all the controls and I’ll use a reference to the form to add the validation controls. When I identify my required fields I’ll also change the backcolor to something other than white to identify that they are required.

Public Module PageControls
 Public Sub SetValidators(ByRef objCell As TableCell, ByRef objForm As HtmlForm)
  'loop through the controls and set validators based on the ValidationGroup
  For Each ctrl As Control In objCell.Controls
   Select Case True
    Case TypeOf ctrl Is TextBox
     Dim txtBox As TextBox = CType(ctrl, TextBox)
     With txtBox
      'Required Field Validator
      If .ValidationGroup.ToUpper = "REQUIRED" Then
       .BackColor = Drawing.Color.LightSalmon
       Dim reqValidator As New RequiredFieldValidator
       With reqValidator
        .ID = txtBox.ID & "ReqFieldValidator"
        .ControlToValidate = txtBox.UniqueID
        .ErrorMessage = "Missing required field!"
        .Text = ""
        .Display = ValidatorDisplay.None
       End With
       objForm.Controls.Add(reqValidator)
      Else
       .BackColor = Drawing.Color.Transparent
      End If
     End With
   End Select
  Next
 End Sub
End Module

I ran into a scenario the other day where I had a Hashtable that I filled with records from a Datatable that had sorted data. Then later in my page code I would fill an asp.net DropDownList using the Hashtable. However, I discovered that the sorted data that I stuck in the Hashtable was not filling the DropDownList in the same sorted order. In fact the order didn’t seem to make sense.

I started looking around for a different way to accomplish what I was doing. I came across the SortedList which is similar to the Hashtable. The SortedList stores items as key value pairs and automatically sorts the list by key. Well, that was almost what I needed. I needed it to sort by value.

Fortunately this was easily remedied by changing how I filled the SortedList. When I fill the list I swap the key and the value. Notice the example below:

The default use of the SortedList is like so: myList.Add(Key as Object, Value as Object)

Instead I add the value as the key and the key as the value.

Dim myList as SortedList
Dim strKey as String = “a key”
Dim strValue as String = “a value”
myList.Add(strValue, strKey)

Then I can just bind the SortedList to my DropDownList and specify that the Key column of the SortedList item is assigned to the DataTextField, and the Value column of the item is assigned to the DataValueField.

myDropDown.DataSource = objList
myDropDown.DataTextField = "Key"
myDropDown.DataValueField = "Value"
myDropDown.DataBind()

This gives me a sorted DropDownList. This of course is not ideal for every scenario. I mostly bind datatables to dropdownlists. However, in this one case, my application was set up differently where this type of implementation was ideal.

In small ASP.NET 2.0 web sites, when membership services is being used, developers may sometimes want to set the visibility of a button or other control based on the role of the logged in user. One simple way to do this is by using code similar to the following.

<asp:ImageButton ID="ibtnSubmit" runat="server" PostBackUrl="~/Feedback.aspx" Visible='<%# CBool(HttpContext.Current.User.IsInRole ("Administrators")) %>' />

This technique works well if you are using a DataList or GridView and you want to be able to set the visibility of specific controls in each row based on roles. Of course, this only works well when the visibility pertains to one role. If you wanted to set the visibility of a control based on more than one role, you could use a Protected function in place of the IsInRole function above. It would look something like the following.

In codebehind:
 Protected Function IsVisible() As Boolean
  Dim aryRoles As String() = Roles.GetRolesForUser()
  If aryRoles.Length = 0 Then Return False
  For i As Integer = 0 To aryRoles.Length
   Select Case aryRoles(i).ToUpper
    Case "ADMINISTRATORS"
     Return True
    Case "FRIENDS"
     Return True
   End Select
  Next
 End Function

On the page:
<asp:ImageButton ID="ibtnSubmit" runat="server" PostBackUrl="~/Feedback.aspx" Visible='<%# IsVisible() %>' />

This instruction is for the programmer that doesn’t really care to hear about the nuts and bolts of adding profile properties to membership users, but just wants the quick read on what to do. I’m assuming that you’re already using the ASP.NET 2.0 membership services.

Adding custom properties for users is really quite simple. In the web.config you define your properties in the <system.web> section like the following code.
   <profile>
      <properties>
         <add name="FirstName"/>
         <add name="LastName"/>
         <add name="Address1"/>
         <add name="Address2"/>
         <add name="City"/>
         <add name="State"/>
         <add name="Zip" />
         <add name="PhoneNumber"/>
      </properties>
   </profile>

Once you have defined your properties in the web.config, the properties magically become accessible through the ProfileCommon class. The ProfileCommon class is only available after adding the Profile section to the web.config.

Now that you have defined the additional properties for users, you can now set and retrieve these properties.

You would probably want to set the properties when creating the user or editing a user’s information. For this purpose you could use code similar to the following. Notice you need to call the Save after you set the properties.

Dim userProfile As ProfileCommon = ProfileCommon.Create(CreateUserWizard1.UserName, True)

With userProfile
   .FirstName = txtFirstName.Text.Trim
   .LastName = txtLastName.Text.Trim
   .Address1 = txtAddress1.Text.Trim
   .Address2 = txtAddress2.Text.Trim
   .City = txtCity.Text.Trim
   .State = drpState.SelectedItem.Value
   .Zip = txtZip.Text.Trim
   .PhoneNumber = txtPhoneNumber.Text.Trim
   .Save()
End With

You can then retrieve information for a user using code similar to the following.

Dim userProfile As ProfileCommon = ProfileCommon.Create(HttpContext.Current.User.Identity.Name, True)

            Dim strFirstName As String = userProfile.FirstName
            Dim strLastName As String = userProfile.LastName
            Dim strCompany As String = userProfile.Company
            Dim strAddress1 As String = userProfile.Address1
            Dim strAddress2 As String = userProfile.Address2
            Dim strCity As String = userProfile.City
            Dim strState As String = userProfile.State
            Dim strZip As String = userProfile.Zip
            Dim strPhoneNumber As String = userProfile.PhoneNumber

You could then display this information on an administration page.

That’s all there is to it. For a working example including a page to manage user information, you can register and download my User Management example project.