Hidden input for Dictionary<string, string> in ASP.NET MVC 3

asp.net-mvc, asp.net-mvc-3, dictionary, hidden-field

Solution

You need two hidden fields one for the `Key` and one for the `Value` if you want to modelbind to a dictionary:

var index = 0;
foreach (var item in Model.ViewPart.Flags)
{

    <input type="hidden" value="@item.Key" 
                         name="ViewPart.Flags[@(index)].Key"/>
    <input type="hidden" value="@item.Value" 
                         name="ViewPart.Flags[@(index)].Value"/>

    index++;
}
    <input type="submit" value="Save"/>

Note, you will be also need a running index to make the model binder happy.

Or if you don't want to have a running you can solve with an addtional hidden `Index` field:

foreach (var item in Model.ViewPart.Flags)
{

    <input type="hidden" value="@item.Key" 
                         name="ViewPart.Flags.Index"/>
    <input type="hidden" value="@item.Key" 
                         name="ViewPart.Flags[@(item.Key)].Key" />
    <input type="hidden" value="@item.Value" 
                         name="ViewPart.Flags[@(item.Key)].Value" />
}
    <input type="submit" value="Save"/>
}

You can find a lots of info about modelbinding with collections in this two article:

- ASP.NET Wire Format for Model Binding to Arrays, Lists, Collections, Dictionaries

- Model Binding To A List

Problem

I need to get my model properties in Post action, so need to hidden element for them, but I have a problem with type of `Dictionary <string, string>`. this is My model: ``` public class ViewModel{ ... public ViewPart ViewPart { get; set; } } public class ViewPart { ... public Dictionary<string, string> Flags { get; set; } } ``` And My Controller: ``` Dictionary<string, string> flags = new Dictionary<string, string>(); flags.Add("kind", "Edit"); flags.Add("Command", "Save"); ViewModel model = new ViewModel(){ Flags = flags }; return View(model); ``` In View: ``` @foreach(var item in Model.ViewPart.Flags) { <input type="hidden" id="ViewPart_Flags_@(item.Key)" value="@item.Value" name="ViewPart.Flags[@(item.Key)]" /> } ``` Also I try This one : ``` @foreach(var item in Model.ViewPart.Flags) { @Html.HiddenFor(modelItem => item) } ``` Update Post Action: ``` [HttpPost] public ActionResult MyPostAction(ViewModel model){ //model.ViewPart.Flags is null } ``` But in Post action the `Flags` is Always null, why? where is my fault? Is there any better way to pass variables from View To Action?

Original source