ASP.NET MVC 3 Razor recursive function

Question

Okay, so I want to display a list containing lists of lists of lists...

I have no way of knowing how many levels there are to display, so I figured this is where I break out the old recursive routine.

I'm having trouble with exactly how to go about this though.

This is what I have so far (in view - simplified):

@foreach(MyObject item in @Model.ListOfObjects){ 
    <div> @item.Title </div>
    //Call recursive function?
}

Now each of these objects also have a List<MyObject>. I want to display each level below this div, with a tab indent per level for instance.

I was thinking a Razor function would be the thing to do here, but I need some help in forming it. Here's my thinking:

@functions{
    public static void ShowSubItems(MyObject _object){
         if(_object.ListOfObjects.Count>0){
             foreach(MyObject subItem in _object.listOfObjects){

                 // Show subItem in HTML
                 ShowSubItems(subItem);
             }
         }
     }
 }

But as you can see, I plainly need some help :)

Paolo Moretti · Accepted Answer · 2012-06-30 09:26:06Z

219

The Razor view engine allows to write inline recursive helpers with the @helper keyword.

@helper ShowTree(IEnumerable<Foo> foos)
{
    <ul>
        @foreach (var foo in foos)
        {
            <li>
                @foo.Title
                @if (foo.Children.Any())
                {
                    @ShowTree(foo.Children)
                }
            </li>
        }
    </ul>
}

edited Jun 30, 2012 at 9:26

answered Jun 21, 2011 at 10:34

Paolo Moretti

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7 Comments

vicky Over a year ago

one thing is remaining that it must call on view by @ShowTree(Foos)

Travis J Over a year ago

This works really well. Also may make sense to mention stackoverflow.com/questions/12943245/… for referencing local variables on the cshtml page.

x19 Over a year ago

how can be implemented this code in asp.net core 2? in asp.net core 2, there is no @helper

Paolo Moretti Over a year ago

@Jahan Looks like @helpers are gone in ASP.NET Core. Inline functions are one potential alternative: github.com/aspnet/Razor/issues/715#issuecomment-272890766 but look much less readable!

x19 Over a year ago

@PaoloMoretti When I define it as recursive Func, how can I do it? I want to create a nested comments with recursive Func. This error shows in VS2018 IDE: "Use of unassigned local variable 'FunctionName' local variable 'FunctionName' might not be initialized before accessing"

|

Peter Mortensen · Accepted Answer · 2017-03-09 04:57:05Z

13

I think it is best to create an HTML helper for this. Something like this:

public static string ShowSubItems(this HtmlHelper helper, MyObject _object)
{
     StringBuilder output = new StringBuilder();
     if(_object.ListOfObjects.Count > 0)
     {
         output.Append("<ul>");

         foreach(MyObject subItem in _object.listOfObjects)
         {
             output.Append("<li>");
             output.Append(_object.Title);
             output.Append(html.ShowSubItems(subItem.listOfObjects);
             output.Append("</li>")
         }
         output.Append("</ul>");
     }
     return output.ToString();
}

Then call it like this:

@foreach(MyObject item in @Model.ListOfObjects){
    <div> @item.Title </div>
    @html.ShowSubItems(item)
}

edited Mar 9, 2017 at 4:57

Peter Mortensen

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answered Jun 21, 2011 at 9:26

Edwin de Koning

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Comments

Prashanth vunnam gcs · Accepted Answer · 2021-04-19 17:28:29Z

5

In .Net core Instead of helper tag we have to use @functions. This below code might useful to some people. Here "IssuerData" is my custom object

@{
      ShowTreeData(Model.HierarchyList);
}

    @functions{

  public static void ShowTreeData(IList<IssuerData> issuers)
      {
       <ul>
      @foreach (var i in issuers)
           {
           <li>
            @i.IssuerName
             @if (i.Children.Any())
               {
                 ShowTreeData(i.Children);
               }
            </li>
          }
       </ul>
       }
   }

answered Apr 19, 2021 at 17:28

Prashanth vunnam gcs

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