How to fix a "System.ArgumentException: 'Value cannot be null or empty. Parameter name: name'" in a MVC app?

Question

I've been working on a summer project where we have to create a portfolio web app where someone can look through a number of potential candidates and select the best one. I've created a SQL database and within there is information and how confident they are in a programming language with a number from 0 - 5. I've created the MVC app and tried to create a new candidate but I am getting this error and have no previous experience coding in this language so am unsure on what to do. Here is my code:

@{
    ViewBag.Title = "Create";
}

<h2>Create</h2>


@using (Html.BeginForm()) 
{
    @Html.AntiForgeryToken()
    
    <div class="form-horizontal">
        <h4>Candidate</h4>
        <hr />
        @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        <div class="form-group">
            @Html.LabelFor(model => model.Id, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Id, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Id, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.First_Name, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.First_Name, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.First_Name, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Last_Name, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Last_Name, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Last_Name, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Date_of_birth, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Date_of_birth, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Date_of_birth, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Location, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Location, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Location, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Email, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Email, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Email, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.C__NET___ASP, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.C__NET___ASP, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.C__NET___ASP, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.CSS, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.CSS, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.CSS, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.HTML, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.HTML, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.HTML, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Java, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Java, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Java, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.JavaScript, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.JavaScript, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.JavaScript, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Python, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Python, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Python, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Python_Flask, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Python_Flask, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Python_Flask, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
                <input type="submit" value="Create" class="btn btn-default" />
            </div>
        </div>
    </div>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

Any help to fix this issue or come at this project in another way would be amazing!

Answer 1

It is caused by __ (double underscores) in the variable name C__NET___ASP .
You can use C_NET_ASP or CNetAsp instead to solve the issue.

I found similar error reported for ASP.NET Core: https://github.com/dotnet/aspnetcore/issues/18913