Practical .NET

Set HtmlHelpers Parameters Using Anonymous Objects in ASP.NET

If you're passing an anonymous object to an HtmlHelper method (to ActionLink, for example), you might want to consider using that anonymous object to eliminate one of the other parameters.

When, in an ASP.NET MVC View, you call an HtmlHelper method, you'll frequently find that one of the parameters you can pass is an optional anonymous object called routeValues. When, for example, you call an ActionLink method, you can pass parameters to specify the text to display, along with the names of the controller and the action method to use when constructing the URL in the href attribute. You can also pass an anonymous routeValues containing values to be included in the URL.

In the following code, for example, the last parameter is a routeValues object that specifies two additional values to include in the URL (the second and third parameters are the action method and controller names, respectively):

@Html.ActionLink("My Text", "Index", "Home", New With {.id = "A123", 
  .year = "2017"})

The anchor tag's href attribute will include the action method name, the controller name, and the routeValues values, like this (assuming you're using ASP.NET MVC default routing rules):

<a href="/home/index/A123?year=2017">My Text</a>

You can save yourself a parameter by rolling the controller name into the routeValues object. All you have to do is make sure that you have a property called controller on your routeValues object:

@Html.ActionLink("My Text", "Index", New With {.controller="Home", 
         .id = "A123", 
         .year = "2017"})

If you've divided up your project into areas you can, of course, also include the area name in the routeValues object, keeping everything (except the action method name) in one place.

This pattern doesn't apply to just the ActionLink method, so, if you prefer fewer parameters, you'll find other places where this works.

About the Author

Peter Vogel is a system architect and principal in PH&V Information Services. PH&V provides full-stack consulting from UX design through object modeling to database design. Peter tweets about his VSM columns with the hashtag #vogelarticles. His blog posts on user experience design can be found at http://blog.learningtree.com/tag/ui/.

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