How to fix "Object Reference not set to an instance of an object"

Question

theres values stored in viewbag as shown in the last picture , but error still popped. Help guysssss

Answer 1

Use ViewData to pass an object from a controller to a view in MVC Core. The following links illustrate how to configure the select tag helper.

The Select Tag Helper

https://code-maze.com/select-tag-helper-aspnetcore/

https://www.learnrazorpages.com/razor-pages/tag-helpers/select-tag-helper

Example

public IActionResult Index()
{
    var options = new List<SelectListItem>() { 
        new SelectListItem()
        {
            Text = "Item 1",
            Value = "1"
        },
        new SelectListItem()
        {
            Text = "Item 2",
            Value = "3"
        }
    };

    ViewData["UnitId"] = options;
    return View();
}

View

@model MvcDemo.Models.SelectModel

@{
    ViewData["Title"] = "Index";
}

<h1>Index</h1>

<form>
    <select asp-for="UnitId" class="form-contorl" asp-items="@((List<SelectListItem>)ViewData["UnitId"])">
        <option value="">--Select--</option>
    </select>
</form>

I think there is a bug in your code that populates the select options since the ViewBag is null. If you share your code then we can help you figure that out as well.