System.Data.SqlClient.SqlException：'无法删除数据库。 怎么解决？

Question

I have added a property "password" in my class model User. It's showing in my view Register.cshtml now.

 <form action="~/Users/SaveRegister" method="post">

            @Html.ValidationSummary(true)

            @Html.AntiForgeryToken()
            <div class="editor-label">
                @Html.LabelFor(model => model.user_name)
            </div>
            <div class="editor-field">
                @Html.EditorFor(model => model.user_name)
                @Html.ValidationMessageFor(model => model.user_name)
            </div>

            <div class="editor-label">
                @Html.LabelFor(model => model.password)
            </div>
            <div class="editor-field">
                @Html.EditorFor(model => model.password)
                @Html.ValidationMessageFor(model => model.password)
            </div>
            <p>
                <input type="submit" value="Register" />
            </p>
    </form>

But it's giving the exception in my controller db.Users.Add(User); when I press Register .

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult SaveRegister(Airlineapp.Models.User User, HttpPostedFileBase file)
{

    db.Users.Add(User);
    db.SaveChanges();
    return RedirectToAction("Index");
}

Answer 1

Someone connected to the database. Try to switch to another database and then, to drop it:

Try

SP_WHO to see who connected

and KILL if needed or use using (context db = new context())