Asp.net-mvc – ASP.NET MVC: Custom Html Helpers in Razor

asp.net-mvcasp.net-mvc-3razor

I am having difficulty with Html Helpers when used with Razor. Said helpers worked fine in MVC 2 with the web form view engine. But not in razor. The error I get at runtime is:

Compiler Error Message: CS1502: The best overloaded method match for 'System.Web.WebPages.WebPageExecutingBase.Write(System.Web.WebPages.HelperResult)' has some invalid arguments

Source Error:


Line 1:  @using Wingspan.Web.Mvc;
Line 2:  @Html.IncrementalMenu(MenuBlock.Site)

Expanding the Show Detailed Compiler Output reveals:

d:\...\Views\Shared\MenuTop.cshtml(2,1): error CS1502: The best overloaded method match for 'System.Web.WebPages.WebPageExecutingBase.Write(System.Web.WebPages.HelperResult)' has some invalid arguments
d:\...\Views\Shared\MenuTop.cshtml(2,7): error CS1503: Argument 1: cannot convert from 'void' to 'System.Web.WebPages.HelperResult'

That indicates to me that razor doesn't like my helper, IncrementalMenu, returning void (which works fine in MVC 2 web form engine views).

I get no errors at Compile time, although the line of code (@Html.IncrementalMenu(…)) is red underlined with the following message:

Cannot implicitly convert type 'void' to 'object'

IncrementalMenu is in the Wingspan.Web.Mvc namespace. It's signature is as follows:

public static void IncrementalMenu(this HtmlHelper html, MenuBlock menuBlock)
{
    // Uses an HtmlTextWriter to render a menu from the sitemap
}

I'm blowed if I know what is wrong…

PS:

The MenuBlock parameter is just an enum that identifies how the menu should render. Don't fixate on this as that is fine.

Best Answer

You can call your helper like this:

@{ Html.IncrementalMenu(MenuBlock.Site); }

WebForms syntax

<% Html.IncrementalMenu(MenuBlock.Site); %>

You just call your method, and the return value (if there is any) is ignored.

Code like this expects a return value, and writes the return value to the html stream:

@Html.YourHelper()

Webforms syntax:

<%: Html.YourHelper() %>

The same, if result value != IHtmlString:

<%= Server.HtmlEncode(Html.YourHelper()) %>

Related Solutions

Asp.net-mvc – ASP.NET MVC – Set custom IIdentity or IPrincipal

Here's how I do it.

I decided to use IPrincipal instead of IIdentity because it means I don't have to implement both IIdentity and IPrincipal.

Create the interface

interface ICustomPrincipal : IPrincipal
{
    int Id { get; set; }
    string FirstName { get; set; }
    string LastName { get; set; }
}

CustomPrincipal

public class CustomPrincipal : ICustomPrincipal
{
    public IIdentity Identity { get; private set; }
    public bool IsInRole(string role) { return false; }

    public CustomPrincipal(string email)
    {
        this.Identity = new GenericIdentity(email);
    }

    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

CustomPrincipalSerializeModel - for serializing custom information into userdata field in FormsAuthenticationTicket object.

public class CustomPrincipalSerializeModel
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

if (Membership.ValidateUser(viewModel.Email, viewModel.Password))
{
    var user = userRepository.Users.Where(u => u.Email == viewModel.Email).First();

    CustomPrincipalSerializeModel serializeModel = new CustomPrincipalSerializeModel();
    serializeModel.Id = user.Id;
    serializeModel.FirstName = user.FirstName;
    serializeModel.LastName = user.LastName;

    JavaScriptSerializer serializer = new JavaScriptSerializer();

    string userData = serializer.Serialize(serializeModel);

    FormsAuthenticationTicket authTicket = new FormsAuthenticationTicket(
             1,
             viewModel.Email,
             DateTime.Now,
             DateTime.Now.AddMinutes(15),
             false,
             userData);

    string encTicket = FormsAuthentication.Encrypt(authTicket);
    HttpCookie faCookie = new HttpCookie(FormsAuthentication.FormsCookieName, encTicket);
    Response.Cookies.Add(faCookie);

    return RedirectToAction("Index", "Home");
}

Global.asax.cs - Reading cookie and replacing HttpContext.User object, this is done by overriding PostAuthenticateRequest

protected void Application_PostAuthenticateRequest(Object sender, EventArgs e)
{
    HttpCookie authCookie = Request.Cookies[FormsAuthentication.FormsCookieName];

    if (authCookie != null)
    {
        FormsAuthenticationTicket authTicket = FormsAuthentication.Decrypt(authCookie.Value);

        JavaScriptSerializer serializer = new JavaScriptSerializer();

        CustomPrincipalSerializeModel serializeModel = serializer.Deserialize<CustomPrincipalSerializeModel>(authTicket.UserData);

        CustomPrincipal newUser = new CustomPrincipal(authTicket.Name);
        newUser.Id = serializeModel.Id;
        newUser.FirstName = serializeModel.FirstName;
        newUser.LastName = serializeModel.LastName;

        HttpContext.Current.User = newUser;
    }
}

Access in Razor views

@((User as CustomPrincipal).Id)
@((User as CustomPrincipal).FirstName)
@((User as CustomPrincipal).LastName)

and in code:

    (User as CustomPrincipal).Id
    (User as CustomPrincipal).FirstName
    (User as CustomPrincipal).LastName

I think the code is self-explanatory. If it isn't, let me know.

Additionally to make the access even easier you can create a base controller and override the returned User object (HttpContext.User):

public class BaseController : Controller
{
    protected virtual new CustomPrincipal User
    {
        get { return HttpContext.User as CustomPrincipal; }
    }
}

and then, for each controller:

public class AccountController : BaseController
{
    // ...
}

which will allow you to access custom fields in code like this:

User.Id
User.FirstName
User.LastName

But this will not work inside views. For that you would need to create a custom WebViewPage implementation:

public abstract class BaseViewPage : WebViewPage
{
    public virtual new CustomPrincipal User
    {
        get { return base.User as CustomPrincipal; }
    }
}

public abstract class BaseViewPage<TModel> : WebViewPage<TModel>
{
    public virtual new CustomPrincipal User
    {
        get { return base.User as CustomPrincipal; }
    }
}

Make it a default page type in Views/web.config:

<pages pageBaseType="Your.Namespace.BaseViewPage">
  <namespaces>
    <add namespace="System.Web.Mvc" />
    <add namespace="System.Web.Mvc.Ajax" />
    <add namespace="System.Web.Mvc.Html" />
    <add namespace="System.Web.Routing" />
  </namespaces>
</pages>

and in views, you can access it like this:

@User.FirstName
@User.LastName

How to import a namespace in Razor View Page

Finally found the answer.

@using MyNamespace

For VB.Net:

@Imports Mynamespace

Take a look at @ravy amiry's answer if you want to include a namespace across the app.

Best Answer

Related Solutions

Asp.net-mvc – ASP.NET MVC – Set custom IIdentity or IPrincipal

How to import a namespace in Razor View Page

Related Topic