I have a DropDownList which I populate like below:

Controller

IEnumerable<Category> categories = _db.Category.ToList();

var selectList = _db.Category.Select(i => new SelectListItem()
{
    Text = i.Name,
    Value = i.Id.ToString()
});

ViewBag.categoriesSelectList = selectList;

And use in view like so:

<select asp-for="Category" name="categoryID" asp-items="@ViewBag.categoriesSelectList" >
        <option>Vælg Kategori:</option>
</select>

However, I can't seem to figure out how I can set the already selected value, so the dropdown "starts" on that value. I tried enumerating over the selectList and changing the Selected attribute of the SelectListItem, but it doesn't work since it won't save the changes I make.

Hope my question makes sense :) thanks all.

CodePudding user response：

Option 1:

Modify your code to include Selected property when creating list of SelectListItem items:

var selectList = _db.Category.Select(i => new SelectListItem()
        {
            Text = i.Name,
            Value = i.Id.ToString(),
            Selected = /* Some condition that is true when the current item should be selected  */
        });

Option 2:

Define a view model with structure that might be referenced in the <select> tag:

public class SelectViewModel
{
    public string Category { get; set; }
    public List<SelectListItem> Categories { get; set; } 
}

The action method:

public IActionResult Categories()
{
    var model = new SelectViewModel() ;
    model.Categories = _db.Category.Select(i => new SelectListItem()
        {
            Text = i.Name,
            Value = i.Id.ToString()
        });

    model.Category = ... your_code_to_set_default_selection;

    return View(model);
}

The view:

@model SelectViewModel

<select asp-for="Category" asp-items="@Model.Categories"></select>

Can find some mode information in the documentation: The Select Tag Helper