European ASP.NET 4.5 Hosting BLOG

BLOG about ASP.NET 4, ASP.NET 4.5 Hosting and Its Technology - Dedicated to European Windows Hosting Customer

European ASP.NET 4.5 Hosting - Amsterdam :: ASP.Net 4.5 Strongly Typed Data Controls and Visual Studio 2012

clock June 25, 2013 06:46 by author Scott

In this post I will show you one of great features in ASP.NET 4.5, it is called Strongly Typed Data controls in ASP.NET 4.5.

I will be demonstrating with a hands-on example on Strongly Typed Data controls and how we can have Intellisense and compile type checking using this new feature.

I assume you have downloaded VS 2012 (Express edition will do).I have also downloaded and installed AdventureWorksLT2012 database.You can download this database from the codeplex website.

I will be creating a simple website without using this feature. Then I will show you what the problem is without using this feature.

1) Launch VS 2012. Create a new ASP.Net Web Forms Site. Choose C# as the development language.Give an appropriate name to your site.

2) Now we will add a data access layer to our site in order to fetch some data to the user interface.I will use EF database first approach.

3) Add a new item in your project, an ADO.Net Entity Data Model. I have named it AdventureWorksLT.edmx.Then we will create the model from the database and click Next.Create a new connection by specifying the SQL Server instance and the database name and click OK.Then click Next in the wizard.In the next screen of the wizard select only the Customer table from the database and hit Finish.You will see the Customer entity in the Entity Designer. 

4) Add a new web form to your site.Name is Customer.aspx.We will add a new web server control a GridView that will get the data from the database through EF.

This is the code for the web server control.I am using the Bind syntax.We are using strings to represent the property names (FirstName,LastName).

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false">

            <Columns>
                <asp:TemplateField HeaderText="FirstName">
                   
                    <ItemTemplate>
                        <asp:Label ID="lblName" runat="server" Text='<%# Bind("FirstName") %>'></asp:Label>
                    </ItemTemplate>
               
               </asp:TemplateField>
               
               <asp:TemplateField HeaderText="LastName">
                   

                     <ItemTemplate>
    <asp:Label ID="lbName" runat="server" Text='<%# Bind("LastName")
%>'></asp:Label>
                    </ItemTemplate>

                </asp:TemplateField>

            </Columns>

        </asp:GridView>

5) In the Page_Load event handling routine of the Customer.aspx page type the following code

        AdventureWorks2012Entities ctx = new AdventureWorks2012Entities();

        var query = from cust in ctx.Customers
     
        select new {cust.FirstName,cust.LastName};

        GridView1.DataSource = query.ToList();

        GridView1.DataBind();

6)  Build and Run the application. You will see the data appearing on the page.

7) Now let's do a simple typo.Replace the following line

<asp:Label ID="lbName" runat="server" Text='<%# Bind("LastName") %>'></asp:Label>

with this

<asp:Label ID="lbName" runat="server" Text='<%# Bind("LLastName") %>'></asp:Label>

Build your site. It will compile. The compiler does not know anything . Guess where you will get the exception, at runtime.Run your site and you will get an exception.

8) Let's rewrite the code in the Customers.aspx page.

        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" ItemType="AdventureWorks2012Entities.Customer">

            <Columns>
                <asp:TemplateField HeaderText="FirstName">

                    <ItemTemplate>
                        <asp:Label ID="lblName" runat="server" Text='<%# Item.FirstName %>'></asp:Label>
                    </ItemTemplate>

                </asp:TemplateField>
                <asp:TemplateField HeaderText="LastName">

                    <ItemTemplate>
                        <asp:Label ID="lbName" runat="server" Text='<%# Item.LastName %>'></asp:Label>
                    </ItemTemplate>

                </asp:TemplateField>

            </Columns>

        </asp:GridView>

Now we can tell our application what type of data the control will be bound to using the ItemType 

ItemType="AdventureWorks2012Entities.Customer"

Now we need to alter the code in the template. Have a look at those 2 lines 

  <asp:Label ID="lblName" runat="server" Text='<%# Item.FirstName %>'></asp:Label>
  <asp:Label ID="lbName" runat="server" Text='<%# Item.LastName %>'></asp:Label> 

Now we have compile type checking and Intellisense in our sample application.As we type the compiler informs us if it recognizes the property. This is a great enhancement since I do not want to face exceptions on runtime because of typos. 

9) Build and run your application again. The sample application works fine.

 



European ASP.NET 4.5 Hosting - Amsterdam :: Creating Security System for ASP.NET 4.5

clock June 18, 2013 06:23 by author Scott

First, you noticed you were assigning users to roles that gave them more access than they needed. So you started tailoring roles more specifically and ended up with roles with one user in them. (And at that point, why bother with roles at all?) Finally, you started creating very targeted roles and assigning multiple roles to each user.

That final strategy is moving you to claims-based security: each role really represents a kind of claim. One role says the user is a manager, another that the user is in the Western division, a third that the user can authorize expenditures up to $10,000. The Microsoft .NET Framework 4.5 supports claims-based security directly, but you can create an equivalent system in ASP.NET 4 (either in MVC, Web Forms or Web API) without much trouble.

The first step is to create an object that implements the IPrincipal interface and has properties for the data (claims) that you'll use to authorize requests. A class that implements IPrincipal has to have a property called Identity that returns a GenericIdentity object (which provides the user's name) and a method called IsInRole method that returns True if a user is assigned to a specific role. The user object in Listing 1 does all of that and adds three additional properties (Division, Job and ApprovalLevel).

Listing 1. A custom user object.

Public Class PHVUser
  Implements IPrincipal

  Dim _gi As GenericIdentity
  Dim _roles As New List(Of String)

  Public Sub New(Name As String, Optional Roles As String = "")
    _gi = New GenericIdentity(Name)
    If Roles <> "" And Roles <> String.Empty Then
      For Each rol In Roles.Split(",").
        Select(Function(r) r.Trim()).ToArray
        _roles.Add(rol)
      Next
    End If

  End Sub

  Public Property Division As String
  Public Property Job As String
  Public Property ApprovalLevel As Integer

  Public ReadOnly Property Identity _
    As IIdentity Implements IPrincipal.Identity
    Get
      Return _gi
    End Get
  End Property

  Public Function IsInRole(role As String) _
    As Boolean Implements IPrincipal.IsInRole
    If _roles.Contains(role) Then
      Return True
    Else
      Return False
    End If
  End Function
End Class

To create a user object for a user named "Peter" who's assigned to the roles manager and clerk, you'd use this code:

usr = New PHVUser("Scott", "manager, clark")

Replacing the User

Now you have to get ASP.NET to use your security object. ASP.NET looks for its IPrincipal object in the CurrentPrincipal object of the Thread class and the User property of HttpContext.Current. If you put your object in there, ASP.NET will use it for its default user name and roles authorization.

To get your IPrincipal object into those two spots, you need to create an HTTP module (a class that implements the IHttpModule and IDisposable events) and add it to your site's processing pipeline. ASP.NET will fire the PostAuthenticateRequest event on your module whenever a request comes in to your site. You need to wire up a method to that event in your module's Init event to create and insert your object.

The class begins like this (I've omitted some code that implements the IDisposable interface that Visual Studio will generate for you):

Public Class PHVAuthHttp
  Implements IHttpModule, IDisposable

  Public Sub Init(context As HttpApplication) _
    Implements IHttpModule.Init
    AddHandler context.PostAuthenticateRequest,
      New EventHandler(AddressOf ReplaceUser)
  End Sub

In your method, you need to find out who the current user is so you can create your IPrincipal object for that user. When a user successfully gets through Forms Authentication, they're given a cookie with their name (and some other information) encrypted inside of it. You can grab that cookie and decrypt it like this:

Private Shared Sub ReplaceUser(sender As Object,
                               e As EventArgs)
  Dim authCookie As HttpCookie
  authCookie = HttpContext.Current.Request.Cookies.
               Get(FormsAuthentication.FormsCookieName)
  If authCookie IsNot Nothing Then
    Dim tkt As FormsAuthenticationTicket
    tkt = FormsAuthentication.Decrypt(authCookie.Value)

After you check that everything has worked, you can use the user's name to retrieve information about the user, and create your IPrincipal object and set your properties on it before putting it where ASP.NET will look for it:

If tkt.Name IsNot Nothing AndAlso
   tkt.Name <> String.Empty AndAlso
   tkt.Name <> "" Then
     // ... Retrieve user information into a variable called emp ...
     Threading.Thread.CurrentPrincipal = New PHVUser(tkt.Name) With
                        {.Region = emp.Region,
                         .Job = emp.Job,
                         .ApprovalLevel = 10000}
     HttpContext.Current.User = Threading.Thread.CurrentPrincipal
End If

Because you're doing this on every request, it would be a good idea to put the user's information (my emp variable in the previous example) in ASP.NET Cache and look for it there before going to the database to retrieve it.

Finally, you need to get ASP.NET to use your HTTP module by adding a modules element to your web.config file inside the system.webServer element. Inside the modules element put an add tag. You can set the name attribute to anything you want, but the type attribute must be set to the full name for your class (namespace and class name) followed by the name of the DLL it's in:

<modules>
  <add name="PHVAuth" type="PHVProj.PHVAuthHttp, PHVProj" />
</modules>

Testing Authorization

You can now test for your user's claims in your own code:

Dim usr As PHVUser = TryCast(HttpContext.Current.User, PHVUser)
If usr IsNot Nothing AndAlso
   usr.Region = "West" AndAlso
   usr.ApprovalLevel = 10000 Then

If you're working in ASP.NET MVC you can also create a custom Authorize filter that checks your user. Listing 2 shows an Authorize filter that checks a user's Region and works well in an asynchronous world. You could add it to a method like this:

<DivisionAuthAttribute(Region="West")>

Listing 2. An Authorize filter that checks a user's Region.

<AttributeUsage(AttributeTargets.Class Or AttributeTargets.Method)>
Public Class DivisionAuthAttribute
  Inherits AuthorizeAttribute

  Private Const IS_AUTHORIZED As String = "isAuthorized"
  Private RedirectUrl As String = "~/Error/Unauthorized"

  Public Property Division As String

  Protected Overrides Function AuthorizeCore(
    httpContext As Web.HttpContextBase) As Boolean
    Dim IsAuthorized As Boolean = False
    Dim us As UserSecurity = TryCast(httpContext.User, PHVUser)
    If us IsNot Nothing AndAlso
      Me.Division <> String.Empty AndAlso
      us.Division = Me.Division Then
        httpContext.Items.Add(IS_AUTHORIZED, IsAuthorized)
        Return True
    End If

    httpContext.Items.Add(IS_AUTHORIZED, IsAuthorized)
    Return False
  End Function

  Public Overrides Sub OnAuthorization(
    filterContext As Web.Mvc.AuthorizationContext)
    MyBase.OnAuthorization(filterContext)
    Dim IsAuthorized As Boolean
    If filterContext.HttpContext.Items(IS_AUTHORIZED) _
      IsNot Nothing Then
      IsAuthorized = Convert.ToBoolean(
        filterContext.HttpContext.Items(IS_AUTHORIZED))
    Else
      IsAuthorized = False
    End If
    If IsAuthorized = False AndAlso
       filterContext.RequestContext.HttpContext.
         User.Identity.IsAuthenticated Then
      filterContext.Result = New RedirectResult(RedirectUrl)
    End If
  End Sub
End Class

You can now extend your user object to encompass any information about your user that you need to authorize requests.

 



European ASP.NET Hosting - Amsterdam :: A potentially dangerous Request.Form value was detected from the client

clock June 5, 2013 06:39 by author Scott

This is the error message that sometimes you’ll see on the shared hosting:

Server Error in 'ASP.Net' Application.


A potentially dangerous Request.Form value was detected from the client (TextBox1"=<p>Hello</p>").

Description: Request Validation has detected a potentially dangerous client input value, and processing of the request has been aborted. This value may indicate an attempt to compromise the security of your application, such as a cross-site scripting attack. You can disable request validation by setting validateRequest=false in the Page directive or in the configuration section. However, it is strongly recommended that your application explicitly check all inputs in this case.

Exception Details: System.Web.HttpRequestValidationException: A potentially dangerous Request.Form value was detected from the client (TextBox1="<p>Hello</p>").

Cause

ASP.Net By default validates all input controls for potentially unsafe contents that can lead to Cross Site Scripting and SQL Injections. Thus it disallows such content by throwing the above Exception. By default it is recommended to allow this check to happen on each postback.

Solution

On many occasions you need to submit HTML Content to your page through Rich TextBoxes or Rich Text Editors. In that case you can avoid this exception by setting the ValidateRequest tag in the @Page Directive to false.

<%@ Page Language="C#" AutoEventWireup="true" ValidateRequest = "false"

This will disable the validation of requests for the page you have set the ValidateRequest flag to false. If you want to disable this check throughout your Web Application you’ll need to set it  false in your web.config <system.web> section

<pages validateRequest ="false " />

That’s it. Hope this helps you in getting rid of the above issue.



About HostForLIFE.eu

HostForLIFE.eu is European Windows Hosting Provider which focuses on Windows Platform only. We deliver on-demand hosting solutions including Shared hosting, Reseller Hosting, Cloud Hosting, Dedicated Servers, and IT as a Service for companies of all sizes.

We have offered the latest Windows 2012 Hosting, ASP.NET 4.5 Hosting, ASP.NET MVC 4 Hosting, ASP.NET MVC 5 Hosting and SQL 2014 Hosting.


Tag cloud

Sign in