MVC剃刀视图中的整数扩展

Question

I am all new with ASP.NET MVC and Extension methods.

I have created two Extensions that i want to use in my View:

public static class Extensions
{
    public static string ToYesNo(this bool value)
    {
        return value ? "Yes" : "No";
    }

    public static string MonthToString(this int value)
    {
        return (value >= 1 && value <= 12) ? CultureInfo.CurrentCulture.DateTimeFormat.GetMonthName(value) : "";
    }
}

I can use ToYesNo with a bool in the View, but i cannot view MonthToString with an integer. I get:

'int' does not contain a definition for 'MonthToString'

The Extensions are in a namespace called BitvaerkAdmin.Models, and i reference that in th cshtml file.

Why can't i use my integer extension?

Edit:

I reference the extensions in my view like this:

@using BitvaerkAdmin.Models


<h3>
    @ViewBag.Month.MonthToString()
</h3>



@foreach (Order order in ViewBag.Orders)
{
    <td>
    @order.Valid.ToYesNo()
    </td>
}

Answer 1

OK, now that you have shown your code it is clear why it doesn't work. You use ViewBag ( the root of all evil in ASP.NET MVC and the origin of all problems that people are having - little addition from the author of this answer).

Once you borrow its path the fall to the abyss is eminent. This fall will be accelerated by the cast that you need to perform in order to make it work:

@((int)(ViewBag.Month).MonthToString())

Simply try running the following console application and you will understand that dynamic variables cannot be used to dispatch extension methods:

public static class Extensions
{
    public static string MonthToString(this int value)
    {
        return (value >= 1 && value <= 12) ? CultureInfo.CurrentCulture.DateTimeFormat.GetMonthName(value) : "";
    }
}

class Program
{
    static void Main()
    {
        dynamic foo = 123;
        Console.WriteLine(foo.MonthToString()); // crash at runtime
    }
}

See why I always critique ViewBag when I see people using it? Because it leads you to all kind of strange things. You lose Intellisense, you cannot dispatch extension methods on dynamic variables, ...

So actually you don't need to cast. You shouldn't use any ViewBag/ViewData at all. You should be using strongly typed view models:

@using BitvaerkAdmin.Models
@model MyViewModel

<h3>
    @Model.Month.MonthToString()
</h3>

@foreach (Order order in Model.Orders)
{
    <td>
        @order.Valid.ToYesNo()
    </td>
}

and to avoid the foreach loop you could use display templates:

@using BitvaerkAdmin.Models
@model MyViewModel

<h3>
    @Model.Month.MonthToString()
</h3>

@Html.DisplayFor(x => x.Orders)

and then define a display template for the order which will automatically be rendered by the framework for all elements of the collection ( ~/Views/Shared/DisplayTemplates/Order.cshtml ):

@using BitvaerkAdmin.Models
@model Order
<td>
    @Model.Valid.ToYesNo()
</td>

Everything is now strongly typed and working.

Answer 2

After giving reference of Extention class in My view I tried as below and it worked for me.

    @using NameSpace Of your Extentions class;
    @{
      int i = 10;          
    }
    <span>@i.MonthToString()</span>