Creating custom helper available in views

问题

I have too much text utility methods, like MakeShortText(string text, int length), RemoveTags(string text), TimeAgo(DateTime date) and other. I want to access them from separate helper like in next example:

@Text().MakeShortText(Model.Text, 10)

Is it possible to create such extension? Or I have to make extension for HtmlHelper like this:

@Html.Text().MaksShortText(Model.Text, 10)

?

回答1:

You could start by defining a custom TextHelper:

public class TextHelper
{
    public TextHelper(ViewContext viewContext)
    {
        ViewContext = viewContext;
    }

    public ViewContext ViewContext { get; private set; }
}

and then have all your methods be extension methods of this TextHelper:

public static class TextHelperExtensions
{
    public static IHtmlString MakeShortText(
        this TextHelper textHelper, 
        string text,
        int value
    )
    {
        ...
    }
}

Then you could define a custom web page:

public abstract class MyWebViewPage<T> : WebViewPage<T>
{
    public override void InitHelpers()
    {
        base.InitHelpers();
        Text = new TextHelper(ViewContext);
    }

    public TextHelper Text { get; private set; }
}

then in your ~/Views/web.config (not in ~/web.config) configure this custom web page as base page for your Razor views using the pageBaseType attribute:

<pages pageBaseType="AppName.Web.Mvc.MyWebViewPage">
    <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 then in your views you will be able to use:

@Text.MakeShortText(Model.Text, 10)

And if you wanted to use the following syntax as shown in your question:

@Text().MakeShortText(Model.Text, 10)

simply modify the custom view engine so that Text is not a property but a method that will return an instance of the TextHelper. Or even return the HtmlHelper instance so that you don't need to move your existing extension methods to TextHelper:

public abstract class MyWebViewPage<T> : WebViewPage<T>
{
    public HtmlHelper Text()
    {
        return Html;
    }
}

---

The second syntax is also possible:

@Html.Text().MaksShortText(Model.Text, 10)

Simply define a custom Text() extension for the HtmlHelper class:

public static class HtmlExtensions
{
    public static TextHelper Text(this HtmlHelper htmlHelper)
    {
        return new TextHelper(htmlHelper.ViewContext);
    }
}

and then the same way as in the first case you would have your custom methods be extension methods of this TextHelper class.

来源：https://stackoverflow.com/questions/9148662/creating-custom-helper-available-in-views