I am currently trying to combine the Html Helper functions DropDownListFor and ValidationMessageFor. I am using asp.Net MVC 5 and have generated a model. My goal is to have an HTML select-box, which is generated by the function DropDownListFor. This should be linked to my model. It is assumed that the client enters something into the field in the frontend in the select-box. If the client doesn't enter anything and clicks on the submit button of my form, the ValidationMessageFor function should be used to display the error text I entered in the model. Of course the form shouldn't be valid and the client shouldn't be allowed to continue as long as nothing is selected in the select-box. That's the theory.
As already mentioned, I have created a model. It looks like this:
public class ExampleModel
{
[Required(ErrorMessage="Test-Error-Text")]
public string salutation { get; set; }
}
I set the values in the select-box in the controller as follows:
var collection = new ListItemCollection();
collection.Add(new ListItem("Mr"));
collection.Add(new ListItem("Mrs"));
collection.Add(new ListItem("unknown"));
collection.Add(new ListItem("company"));
var selList = new SelectList(collection, "Salutation");
ViewBag.Salutation = selList;
Then I call the functions in the view as follows:
@Html.DropDownListFor(Model=> Model.salutation, ViewBag.Salutation as SelectList, "", new { @class="adrInput form-control"})
@Html.ValidationMessageFor(Model=>Model.salutation)
As this is currently, I get the following exception when submitting:
System.InvalidOperationException: 'There is no ViewData item of type 'IEnumerable<SelectListItem>' that has the key 'salutation'.'
I have almost never worked with these Html Helper functions. Something is wrong here. I'm grateful for any help.
I found the mistake. I have to return the model to the view after submitting the form, if the form is not valid. Furthermore I have to initialize the SelectList for the ViewBag again. Somehow the values get lost in ViewBag.Salutation after validation.