Why doesn't My ModelState.IsValid return true in Asp.Net MVC4?

Question

I have a controller that looks like this:

[HttpPost] [Authorize(Roles = "Admin")] public ActionResult ProjectAdd(PortfolioViewModel model, int[] categories, HttpPostedFileBase thumbnail, HttpPostedFileBase image) { model.ProjectImage = System.IO.Path.GetFileName(image.FileName); model.ProjectThubmnail = System.IO.Path.GetFileName(thumbnail.FileName); using (PortfolioManager pm = new PortfolioManager()) { using (CategoryManager cm = new CategoryManager()) { if (ModelState.IsValid) { bool status = pm.AddNewProject(model, categories); } ViewBag.Categories = cm.GetAllCategories(); ViewBag.ProjectsList = pm.GetAllProjects(); } } return View(model); } 

My view:

 @using (Html.BeginForm("projectAdd", "home", FormMethod.Post, new { enctype = "multipart/form-data" })) { @Html.ValidationSummary(true) <fieldset> <legend>Add New Project</legend> <div class="editor-label"> @Html.LabelFor(model => model.ProjectHeading) </div> <div class="editor-field"> @Html.EditorFor(model => model.ProjectHeading) @Html.ValidationMessageFor(model => model.ProjectHeading) </div> <div class="editor-label"> @Html.LabelFor(model => model.ProjecctUrl) </div> <div class="editor-field"> @Html.EditorFor(model => model.ProjecctUrl) @Html.ValidationMessageFor(model => model.ProjecctUrl) </div> <div class="editor-label"> @Html.LabelFor(model => model.ProjectLongDescription) </div> <div class="editor-field"> @Html.EditorFor(model => model.ProjectLongDescription) @Html.ValidationMessageFor(model => model.ProjectLongDescription) </div> <div class="editor-label"> @Html.LabelFor(model => model.PromoFront) </div> @Html.EditorFor(model => model.PromoFront) @Html.ValidationMessageFor(model => model.PromoFront) <div class="editor-label"> <label for="thumbnail">Thumbnail</label> </div> <div class="editor-field"> <input type="file" name="thumbnail" id="thumbnail" /> </div> <div class="editor-label"> <label for="image">Image</label> </div> <div class="editor-field"> <input type="file" name="image" id="image" /> </div> <div class="editor-label"> <label for="categories">Categories</label> </div> @foreach (var c in categories) { <input type="checkbox" name="categories" value="@c.CategoryId"> @c.CategoryName } <p> <input type="submit" value="Create" class="submit" /> </p> </fieldset> } 

When I try to use this code, the ModeState.IsValid property becomes false (I saw through debugging). However, when I delete ModeState.IsValid , the insert is successful and everything works exactly the way I want.
I need the ModeState.IsValid property to validate my view.

Updated: My view model:

 [Key] public int ProjectId { get; set; } [Required(ErrorMessage="Please enter project heading")] public string ProjectHeading { get; set; } [Required(ErrorMessage = "Please enter project Url")] public string ProjecctUrl { get; set; } [Required(ErrorMessage = "Please enter project description")] public string ProjectLongDescription { get; set; } public string ProjectShortDescription { get { var text = ProjectLongDescription; if (text.Length > ApplicationConfiguration.ProjectShortDescriptionLength) { text = text.Remove(ApplicationConfiguration.ProjectShortDescriptionLength); text += "..."; } return text; } } public bool PromoFront { get; set; } [Required(ErrorMessage = "You must sepcify a thumbnail")] public string ProjectThubmnail { get; set; } [Required(ErrorMessage = "You must select an image")] public string ProjectImage { get; set; } public int CategoryId { get; set; } public IEnumerable<Category> Categories { get; set; } 

Updated 2: I found an error. problem

 {System.InvalidOperationException: The parameter conversion from type 'System.String' to type 'PortfolioMVC4.Models.Category' failed because no type converter can convert between these types. at System.Web.Mvc.ValueProviderResult.ConvertSimpleType(CultureInfo culture, Object value, Type destinationType) at System.Web.Mvc.ValueProviderResult.UnwrapPossibleArrayType(CultureInfo culture, Object value, Type destinationType) at System.Web.Mvc.ValueProviderResult.ConvertTo(Type type, CultureInfo culture) at System.Web.Mvc.DefaultModelBinder.ConvertProviderResult(ModelStateDictionary modelState, String modelStateKey, ValueProviderResult valueProviderResult, Type destinationType)} 

Answer 1

When debugging, check for ModelState errors. This is a key / value dictionary with all the properties necessary for a model to be valid. If you check Values -property, you can find the value with Errors -list which is not empty and see what the error is.

Or add this line of code to the action method to get all errors for the model:

 var errors = ModelState.Where(v => v.Value.Errors.Any()); 

Answer 2

You need to rename your categories action parameter to another, because your PortfolioViewModel model already has a property with the name categories , which has a completely different type and which disrupts the model change:

 [HttpPost] [Authorize(Roles = "Admin")] public ActionResult ProjectAdd( PortfolioViewModel model, int[] categoryIds, HttpPostedFileBase thumbnail, HttpPostedFileBase image ) { ... } 

Now, obviously, you will also have to update your view to match the flag name.

Although this may solve your problem, I highly recommend that you use view models and stop transferring your domain models to views.