Jason Jung

My New Personal Blog Launched

Jason Jung — Fri, 21 Mar 2008 06:00:00 GMT

My blog moved to a pesonal site that I built using ASP.NET MVC Preview 2.

Extending SiteMapProvider to handle the visibility of Role-based links

Jason Jung — Mon, 16 Apr 2007 21:05:00 GMT

By default, the roles used in SiteMapNode's cannot be used to restrict access to certain roles. The actual security checks are done at the web.config level using <authorization> and allow and deny tags.

If we want the sitemap to purely handle the visibility of the links based on roles, we can extend the SiteMapProvider and override only one method to achieve this. We can simply create a file that extends from a variety of builit-in SiteMap providers including the abstract class, SiteMapProvider where you'd have to override and implement the basic functionalities for building the SiteMapNodes. You can also derive from the StaticSiteMapProvider class, which is a partial implementation of the SiteMapProvider class with additional methods: AddNode, RemoveNode, BuildSiteMap, and Clear.

In our scenario, we can simply derive from the XmlSiteMapProvider where we have the full functionalities of the SiteMap and we simply need to override the methods we want to.

One method we're going to override is the IsAccessibleToUser method which determines the visibility of the current node.

public class CustomSiteMapProvider : XmlSiteMapProvider
{
    public CustomSiteMapProvider()
    {
        //
        // TODO: Add constructor logic here
        //
    }


    public override bool IsAccessibleToUser(HttpContext context, SiteMapNode node)
    {
        bool isAccessible = false;
        if (node.Roles.Count == 0)
            return true;

        foreach (object role in node.Roles)
        {
            if (context.User.IsInRole(role.ToString()))
            {
                isAccessible = true;
                break;
            }
        }

        return isAccessible;
    }


}

This will make the nodes visible to the users with the roles defined in the SiteMapNode AND it will make them invisible to the users who do not belong to the roles defined in the SiteMapNode.

Now we just need to modify the web.config file to change the default SiteMapProvider to our own custom provider.

description="Custom SiteMap Provider" type="CustomSiteMapProvider" siteMapFile="Web.sitemap" securityTrimmingEnabled="true"/>

</providers>

</siteMap>

ASP .NET 2.0 Accessing Parent Pages from User Controls

Jason Jung — Wed, 13 Sep 2006 01:32:00 GMT

I recently ran into a problem when I was trying to access properties in a parent page from a user control.

If I have my parent page, MyPage.aspx under the root folder, and my user control, MyControl.ascx in a sub-folder called Controls, in ASP .NET 1.x, the following was possible.

public partial class MyPage

{

private string myString;

public string MyString

{

get { return myString; }

}

void Page_Load(object sender, EventArgs e)

{

myString = “my string”;

}

public partial class Controls_MyControl

{

protected void Page_Load(object sender, EventArgs e)

{

string myString = ((MyPage)this.Page).MyString;

}

This way of accessing the properties in the parent’s page worked just fine. But if you try to build this project, you will get a compilation error saying MyPage could not be found in the assembly.

This is no longer possible because of the nature of the .NET 2.0 compiler. Partial classes will be compiled at run time, and each sub directory will be placed into different assemblies. This is why MyPage in my example was not visible to MyControl, which resides in a different directory.

In order to work around this problem, you’d have to utilize the App_Code folder so that your parent page will inherit from a base page, and the base page will contain the properties. This way, you can cast your parent page into the PageBase. in your user control to access the properties.

public partial class Controls_MyControl

{

protected void Page_Load(object sender, EventArgs e)

{

string myString = ((PageBase)this.Page).MyString;

}

I had a similar problem with dynamically loaded user controls when I tried to cast them back to their own class because those user controls were in a different directory. In this case, I’ve seen a workaround that requires the <% Register > tag for the dynamically loaded user controls on the page.

I wonder if there’s a better workaround, or the right way to get around this problem,

Custom Configuration Section Handler in .NET 2.0

Jason Jung — Tue, 08 Aug 2006 15:18:00 GMT

I recently had to deal with creating custom sections in the web/app.config file. In the .NET 1.x realm, I had to create a section handler which implements public class CustomSectionHandler: IConfigurationSectionHandler.

In 2.0, we have to create a custom section handler that derives from ConfigurationSection, which then can be used to contain public properties that map the attributes in the configuration file.

For example, Let's say that we have the following custom section in web.config:

MySection Attribute1="1" Attribute2="x" />

We can write a custom section like the following:

using System.Configuration;

public class MyConfigSection: ConfigurationSection

{

[ConfigurationProperty("Attribute1", IsKey = true, IsRequired = true)]

public int Attribute1

{

get { return (int)this["Attribute1"]; }

set { this["Attribute1"] = value; }

}

[ConfigurationProperty("Attribute2")]

public string Attribute2

{

get { return (string)this["Attribute2"]; }

set { this["Attribute2"] = value; }

}

If you want to support mutiple elements within a config section, you can do so by creating another class that derives from ConfigurationElementCollection to maintain a collection of the configuration element. We can tweak the custom section in the web.config file a little bit to support this.

MyConfigSection>

Employees>

Employee EmployeeID="alincoln" FirstName="abraham" LastName="lincoln" />

Employee EmployeeID="gwashington" FirstName="george" LastName="washington" />

Employee EmployeeID="gbush" FirstName="george" LastName="bush" />

Employees>

MyConfigSection>

Then, we can write the custon section like this:

public class MyConfigSection: ConfigurationSection

{

[ConfigurationProperty("Employees", IsDefaultCollection = true)]

public EmployeeCollection Employees

{

get { return (EmployeeCollection) base["Employees"]; }

}

public sealed class EmployeeElement : ConfigurationElement

{

[ConfigurationProperty("EmployeeID", IsKey = true, IsRequired = true)]

public string EmployeeID

{

get { return (string)this["EmployeeID"]; }

set { this["EmployeeID"] = value; }

}

[ConfigurationProperty("FirstName", IsRequired = true)]

public string FirstName

{

get { return (string)this["FirstName"]; }

set { this["FirstName"] = value; }

}

[ConfigurationProperty("LastName", IsRequired = true)]

public string LastName

{

get { return (string)this["LastName"]; }

set { this["LastName"] = value; }

}

public sealed class EmployeeCollection : ConfigurationElementCollection

{

protected override ConfigurationElement CreateNewElement()

{

return new EmployeeElement();

}

protected override object GetElementKey(ConfigurationElement element)

{

return ((EmployeeElement)element).EmployeeID;

}

public override ConfigurationElementCollectionType CollectionType

{

get { return ConfigurationElementCollectionType.BasicMap; }

}

protected override string ElementName

{

get { return "EmployeeElement"; }

}

public EmployeeElement this[int index]

{

get { return (EmployeeElement)BaseGet(index); }

set

{

if (BaseGet(index) != null)

{

BaseRemoveAt(index);

}

BaseAdd(index, value);

}

new public EmployeeElement this[string employeeID]

{

get{return (EmployeeElement)BaseGet(employeeID);}

}

public bool ContainsKey(string key)

{

bool result = false;

object[] keys = BaseGetAllKeys();

foreach (object obj in keys)

{

if ((string)obj == key)

{

result = true;

break;

}

return result;

}

I've added the ContainsKey() Method to the EmployeeCollection class because I couldn't find a simpler way to check for the existence of a given key. Maybe there is a better solution..

Now you need to add the custom section to the ConfigSections in the coniguration file.

section name="MyConfigSection" type="Namespace.ClassName, AssemblyName" />

Lastly, you can access the config section from your code the following way:

MyConfigSection employeeSection=

(MyConfigSection )System.Configuration.ConfigurationManager.GetSection("MyConfigSection");

I hope it helps!