It recently began to annoy me that every time I want to redirect to a page I have to use a string. Not a big deal I know but when you have broken links it can reflect badly on you as a developer, so I began to look for some solution that would allow for the following.

• Refactoring: I need to be able to move a page around without having to find every string reference to it
• No Reflection: It’s slow I don’t want to have to use it when redirects happen often.
• Parameters: I want to be able to pass parameters to a function and make that become part of the get request, I want the logic for that to exist on the page being redirected to as that is where the parameters are being used, this will also help with refactoring, the plain ole redirect logic however would just exist on a base class, don’t want to have to rewrite for every page.

I knew the ideal situation would be if I could somehow use the fact that web application projects use the folder hierarchy for its namespace convention and end up being able to redirect to the page ~/Users/UserDetails.aspx?UserId=14 with the following command Users.UserDetails.Redirect(14);

Here is how I did it:

I have a web application project, let’s call it MyProject.Web

I have two pages called UserDetails.aspx and UserList.aspx in the folder Users.

They both inherit from the following base class:

They follow this pattern:

namespace MyProject.Web.Users

{

public partial class UserDetails: BasePage<UserDetails>

{

public static void Redirect(int userId)

{

Redirect(“UserId=” + userId.ToString());

}

}

}

Now because UserDetails and UserList are in the same folder I can simply call UserDetails.Redirect(selectedUserId) on the UserList and UserList.Redirect() on the UserDetails.
The only real disadvantage is that it could confuse people who discover a Redirect method on their current page that they can’t use to make it to another page.
However it should be abundantly clear to everyone what you are doing when they see it already written.
Also every time you move a class, remove or add a parameter, it will break on compile time not at run time.

Comments and feedback welcome.

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using System;
using System.Collections.Specialized;
using System.Globalization;
using System.IO;
using System.Reflection;
using System.Threading;
using System.Web;
using System.Web.Hosting;
using System.Web.SessionState;

public sealed class MockHttpContext
{
    // NOTE: This code is based on the following article:
    // http://righteousindignation.gotdns.org/blog/archive/2004/04/13/149.aspx
    private const string ContextKeyAspSession = "AspSession";
    private const string ThreadDataKeyAppPath = ".appPath";
    private const string ThreadDataKeyAppPathValue = "c:\\inetpub\\wwwroot\\webapp\\";
    private const string ThreadDataKeyAppVPath = ".appVPath";
    private const string ThreadDataKeyAppVPathValue = "/webapp";
    private const string WorkerRequestPage = "default.aspx";

    private HttpContext context = null;

    private MockHttpContext()
        : base()
    {
    }

    public MockHttpContext(bool isSecure)
        : this()
    {
        Thread.GetDomain().SetData(
            MockHttpContext.ThreadDataKeyAppPath, MockHttpContext.ThreadDataKeyAppPathValue);
        Thread.GetDomain().SetData(
            MockHttpContext.ThreadDataKeyAppVPath, MockHttpContext.ThreadDataKeyAppVPathValue);
        SimpleWorkerRequest request = new WorkerRequest(MockHttpContext.WorkerRequestPage,
            string.Empty, new StringWriter(), isSecure);
        this.context = new HttpContext(request);

        HttpSessionStateContainer container = new HttpSessionStateContainer(
            Guid.NewGuid().ToString("N"), new SessionStateItemCollection(), new HttpStaticObjectsCollection(),
            5, true, HttpCookieMode.AutoDetect, SessionStateMode.InProc, false);

        HttpSessionState state = Activator.CreateInstance(
             typeof(HttpSessionState),
             BindingFlags.Public | BindingFlags.NonPublic |
             BindingFlags.Instance | BindingFlags.CreateInstance,
             null,
             new object[] { container }, CultureInfo.CurrentCulture) as HttpSessionState;
        this.context.Items[ContextKeyAspSession] = state;
    }

    public HttpContext Context
    {
        get
        {
            return this.context;
        }
    }

    private class WorkerRequest : SimpleWorkerRequest
    {
        private bool isSecure = false;

        public WorkerRequest(string page, string query, TextWriter output, bool isSecure)
            : base(page, query, output)
        {
            this.isSecure = isSecure;
        }

        public override bool IsSecure()
        {
            return this.isSecure;
        }
    }
}

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Here is how to call a method with an out parameter using MethodInfo.Invoke, in this case the out parameter is the last one (int).

int parNum = 0;
string parText = “99″;
object[] methodParms = new object[] { parText, parNum };

MethodInfo methInfo = parNum.GetType().GetMethod(“TryParse”, new Type[] { typeof(string), typeof(int).MakeByRefType() });
methInfo.Invoke(null, methodParms);
parNum = (int)methodParms[1];
Console.WriteLine(“Parsed number:{0}”, parNum);

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I picked up a bit of code from http://www.west-wind.com/Weblog/posts/154812.aspx to handle it, but had to make some changes to make it work in a more generic fashion. My change is small and in bold.

/// <summary>

/// Returns a site relative HTTP path from a partial path starting out with a ~.

/// Same syntax that ASP.Net internally supports but this method can be used

/// outside of the Page framework.

///

/// Works like Control.ResolveUrl including support for ~ syntax

/// but returns an absolute URL.

/// </summary>

/// <param name=”originalUrl”>Any Url including those starting with ~</param>

/// <returns>relative url</returns>

public static string ResolveUrl(string originalUrl)
{

if (originalUrl == null)

return null;

// *** Absolute path – just return

if (originalUrl.IndexOf(“://”) != -1)

return originalUrl;

// *** Fix up image path for ~ root app dir directory

if (originalUrl.StartsWith(“~”))
{

string newUrl = “”;

if (HttpContext.Current != null)

newUrl = HttpContext.Current.Request.Url.Scheme + “://” + HttpContext.Current.Request.Url.Host + HttpContext.Current.Request.ApplicationPath + originalUrl.Substring(1).Replace(“//”, “/”);

else

// *** Not context: assume current directory is the base directory

throw new ArgumentException(“Invalid URL: Relative URL not allowed.”);

// *** Just to be sure fix up any double slashes

return newUrl;

}

return originalUrl;

}

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System.Reflections allows you to search for the relevant method by descibing what it looks like

using System.Reflection;
...
public InnerMethod(Object x)
{
MethodInfo methodInfo = entity.GetType().GetMethod( "InnerMethod", new Type[] { x.GetType() });
if(methodInfo != null)
{
methodInfo.invoke(this,Invoke(null, new object[] { x }) ;
}
// Generic Actions
}


Now every time you add or remove a method, you only have to add or remove it in one place.

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