Post Form MVC with List of List

Question

Most of the Tutorials, Questions I found online where about when the Model has one List of Items. But In my Case I have a List of Items which further have a List of Items.

Answer 1

Its fairly simple - you just need to nest 2 for loops in the view (don't use foreach)

ie change to:

@Html.BeginForm(){

@for(int j = 0; j < Model.Items.Count; j++)
{
    
@Model.Items[j].ItemAId
    @Html.HiddenFor(m => m.Items[j].ItemAId)  
    @* (don't forget this!) *@


    for (int i = 0; i < Model.Items[j].ItemBList.Count; i++)
    {
        @Html.HiddenFor(m => m.Items[j].ItemBList[i].ItemBId )

        @Html.TextBoxFor(m => m.Items[j].ItemBList[i].NewInput)

    }

}
Submit
}

The MVC Model Binder requires form fields representing properties in lists to be named something like [#].property1name, [#].property2name in order to properly associate them to each other during binding after postback. Same principle applies to list properties of listitems. You need to use a for loop rather than a foreach loop to get the right form field names when using HTML helpers!