ValidationMessage in MVC View not displaying - asp.net-mvc

Question

I have a custom date validation and I have done as explained in
this link. Below is my Model code:
[DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}",ApplyFormatInEditMode=true)]
[DisplayName("Sch.Start Date:")]
[DataType(DataType.Date)]
[ValidProjectDate(ErrorMessage="Project Start Date cannot be greater than Project End Date.")]
public DateTime? ProjectScheduleStartDate { get; set; }
[DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}", ApplyFormatInEditMode = true)]
[DisplayName("Sch.End Date:")]
[DataType(DataType.Date)]
[ValidProjectDate(ErrorMessage = "Project End Date cannot be less than or Equal to Current Date.")]
public DateTime? ProjectScheduleEndDate { get; set; }
`
Below is my code in View:
<div class="form-group">
#Html.LabelFor(model => model.ProjectScheduleStartDate, htmlAttributes: new { #class = "control-label col-md-2" })
<div class="col-md-10">
#Html.EditorFor(model => model.ProjectScheduleStartDate, new { htmlAttributes = new { #class = "form-control" } })
#Html.ValidationMessageFor(model => model.ProjectScheduleStartDate, "*", new { #class = "text-danger" })
</div>
</div>
<div class="form-group">
#Html.LabelFor(model => model.ProjectScheduleEndDate, htmlAttributes: new { #class = "control-label col-md-2" })
<div class="col-md-10">
#Html.EditorFor(model => model.ProjectScheduleEndDate, new { htmlAttributes = new { #class = "form-control" } })
#Html.ValidationMessageFor(model => model.ProjectScheduleEndDate, "*", new { #class = "text-danger" })
</div>
</div>
<hr/>
#Html.ValidationSummary(true, "Please correct below errors", new { #class = "text-danger" })
Below is my code in Controller:
if (ModelState.IsValid)
{
ProjectManager pm = new ProjectManager();
pm.AddProjects(prj);
ViewBag.Result = "Record Inserted Successfully.";
ModelState.Clear();
}
else
{
ModelState.AddModelError(string.Empty, "An Error has happened");
}
return View("AddNewProject");
Even though I tried to display the validation message as mentioned in the model class, I am getting only star images instead of the validation messages. However, the Error messsages specified inside the validation summary is getting displayed. But I want to display the messages in the model class. Any clue?

Answer 1

I removed the star symbol on the ValidationMessageFor in View. It started working.. May be helpful for someone.

Answer 2

Your attribute's ValidationResult does not have a key associated with a field, which prevents ValidationMessageFor from working.
I would suggest using implementing the IValidatable interface on your ViewModel instead of your custom data validation attribute, unless there are many places in your application where this type of validation is required.
You will notice that it provides the name of the property as the key to associate the error with the field:
public class TestViewModel : IValidatableObject
{
public DateTime? ProjectStartDate { get; set; }
public DateTime? ProjectEndDate { get; set; }
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
if (ProjectStartDate > ProjectEndDate)
yield return new ValidationResult("The Project Start Date cannot be after the Project End Date.", new List<string>() { nameof(ProjectStartDate) });
if (ProjectEndDate < DateTime.Now)
yield return new ValidationResult("Project End Date cannot be less than or Equal to Current Date.", new List<string>() { nameof(ProjectEndDate) });
}
}