Templates can be used only with field access property access single-dimension array index or single-parameter custom indexer expressions error

Question

Why am I receiving the error      Templates can be used only with field access  property access  single-dimension array index  or single-parameter custom indexer expressions   at this code    model IEnumerable lt ArtSchoolProject Models Trainer gt      ViewBag Title    Index   Layout      Views Shared  PageLayout cshtml       lt h2 gt Index lt  h2 gt    lt p gt   Html ActionLink  Create New    Create    lt  p gt   lt ul class  trainers  gt     foreach  var item in Model     lt li gt     lt div gt         lt div class  left  gt             lt a href   Url Action  Details    Details   new   id   item ID     gt                 lt img src    Images Trainer  item Picture    gt             lt  a gt         lt  div gt         lt div class  right  gt             Html ActionLink item Name  Details  new  id item ID              lt br   gt             Html DisplayFor modelItem  gt  string  item Description ToString   Substring 0 100          lt  div gt     lt  div gt     lt  li gt          lt  ul gt    at line    Html DisplayFor modelItem  gt item Description ToString   Substring 0 100     Update   Problem solved  I added to my code         string parameterValue   item Description ToString   Substring 0  100                           Html DisplayFor modelItem  gt parameterValue    My new code    foreach  var item in Model     lt li gt     lt div gt         lt div class  left  gt             lt a href   Url Action  Details    Details   new   id   item ID     gt                 lt img src    Images Trainer  item Picture    gt             lt  a gt         lt  div gt         lt div class  right  gt             Html ActionLink item Name  Details  new  id item ID              lt br   gt               string parameterValue   item Description ToString   Substring 0  100                           Html DisplayFor modelItem  gt parameterValue         lt  div gt     lt  div gt    lt  li gt      This is only one possibility  Just for curiosity is there another solution for solving the error

User · Answer

I ran into a similar problem with the same error message using following code:

@Html.DisplayFor(model => model.EndDate.Value.ToShortDateString())

I found a good answer here

Turns out you can decorate the property in your model with a displayformat then apply a dataformatstring.

Be sure to import the following lib into your model:

using System.ComponentModel.DataAnnotations;

User · Answer

The template it is referring to is the Html helper DisplayFor   DisplayFor expects to be given an expression that conforms to the rules as specified in the error message   You are trying to pass in a method chain to be executed and it doesn t like it   This is a perfect example of where the MVVM  Model-View-ViewModel  pattern comes in handy   You could wrap up your Trainer model class in another class called TrainerViewModel that could work something like this   class TrainerViewModel       private Trainer  trainer       public string ShortDescription               get                       return  trainer Description ToString   Substring 0  100                        public TrainerViewModel Trainer trainer                 trainer   trainer            You would modify your view model class to contain all the properties needed to display that data in the view  hence the name ViewModel   Then you would modify your controller to return a TrainerViewModel object rather than a Trainer object and change your model type declaration in your view file to TrainerViewModel too

User · Answer

The    For extension methods on the HtmlHelper  e g   DisplayFor  TextBoxFor  ElementFor  etc     take a property and nothing else  If you don t have a property  use the non-For method  e g   Display  TextBox  Element  etc      The    For extension methods provides a way of simplifying postback by naming the control after the property  This is why it takes an expression and not simply a value  If you are not interested in this postback facilitation then do not use the    For methods at all  Note  You should not be doing things like calling ToString inside the view  This should be done inside the view model  I realize that a lot of demo projects put domain objects straight into the view  In my experience  this rarely works because it assumes that you do not want any formatting on the data in the domain entity  Best practice is to create a view model that wraps the entity into something that can be directly consumed by the view  Most of the properties in this view model should be strings that are already formatted or data for which you have element or display templates created

User · Answer

Fill in the service layer with the model and then send it to the view  For example  ViewItem ModelItem ToString   Substring 0 100

User · Answer

I had the same problem with something like    foreach  var item in Model         Html DisplayFor m   gt   item IsIdle   BoolIcon       I solved this just by doing   foreach  var item in Model        var active    item IsIdle       Html DisplayFor m   gt  active    BoolIcon       When you know the trick  it s simple   The difference is that  in the first case  I passed a method as a parameter whereas in the second case  it s an expression

[c#] "Templates can be used only with field access, property access, single-dimension array index, or single-parameter custom indexer expressions" error

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