<button class="button" data-open="categoryModal">Create A Group</button>

    <div class="reveal" id="categoryModal" data-reveal>
        <h1>Create Category</h1>
        @using (Html.BeginForm("CreateCategory", "Home"))
        {
            <input type="text" name="categoryName" />
            <input type="submit" class="button"/>
        }
    </div>

[HttpPost]
    public IActionResult CreateCategory(CategoryVM category)
    {
        if(!ModelState.IsValid) return View(category);

        if (//category already exists)
        {
            ModelState.AddModelError("", "Category exists");
            return View(category);
        }
        _categoryRepository.Insert(new Category { Name = category.Name });
        return RedirectToAction("Index", "Home");
    }