如何从MVC中的radioButtonfor获取唯一ID

Question

I have a below model

public class category
{
    [Key]
    public long category_id { get; set; }
    public string category_desc { get; set; }
    public long? client_id { get; set; }
    public long? display_sno { get; set; }
}

controller passing the model to view

public ActionResult category(long? client_id)
{
    var category_type = db.category.Where(m => m.client_id == null).ToList();
    if(client_id == 10)
    {
        category_type = db.category.Where(m => m.client_id == client_id).ToList();
    }
    return View(category_type);
}

In view populating the radion button

@foreach (var item in Model)                                                 
{ 
    @Html.DisplayFor(modelItem => item.display_sno)<text>.</text> &nbsp;
    @Html.RadioButtonFor(modelItem => item.category_id, item.category_id, new { id=item.category_id})@item.category_desc
}

post Method

public ActionResult Category(category g)
{

}

In post method g is coming as null . What I am missing here?

Answer 1

Your misunderstanding how radio buttons work. They are for binding one of many options to a single property, in the same way a dropdownlist works. Your code is generating radio buttons that bind to itself. And if you inspect the html you will see that it generates name="item.category_id" which would not bind to your model anyway (that would only bind to a model containing a complex object named Item which contained a property named category_id ).

Assuming you have a model for a Product which contained a property for its Category , and you wanted to assign one of the values of your category table to the Category property, then your view models would look like

public class ProductVM
{
    [Required(ErrorMessage = "Please select a category")]
    public int? Category { get; set; }
    public IEnumerable<CategoryVM> CategoryOptions { get; set; }
}

public class CategoryVM
{
    public int ID { get; set; }
    public string Name { get; set; }
}

Note the use of a nullable property for Category is explained in What does it mean for a property to be [Required] and nullable?

Then the controller methods (for a Create view) would look like

public ActionResult Create()
{
    ProductVM model = new ProductVM();
    ConfigureViewModel(model);
    return View(model);
}
public ActionResult Create(ProductVM model)
{
    if (!ModelState.IsValid())
    {
        ConfigureViewModel(model);
        return View(model);
    }
    .... // Initialize your Product data model, set its properties based on the view model
    // Save and redirect
}
private void ConfigureViewModel(ProductVM model)
{
    model.CategoryOptions = db.categories.Select(x => new CategoryVM
    {
        ID = x.category_id,
        Name = x.category_desc
    });
}

Then the view would be

@model ProductVM
....
@using (Html.BeginForm())
{
    @Html.DisplayNameFor(m => m.Category)
    foreach(var category in Model.CategoryOptions)
    {
        <label>
            @Html.RadioButtonFor(m => m.Category, category.ID, new { id = "" })
            <span>@category.Name</span>
        </label>
    }
    @Html.ValidationMessageFor(m => m.Category)
    <input type="submit" .... />
}

Note that the new { id = "" } is removing the id attribute which would otherwise be invalid html because of duplicates.