Model Validation is not appearing in asp.net mvc

Question

I am using Asp.net MVC 4 and .NET 4.5. I have a view where Name of class, class teacher name and List of students in that class are displayed in edit mode. My main view looks like

public class Class
{
    public int ClassId { get; set; }

    public string ClassName { get; set; }

    public string ClassTeacherName { get; set; }

    [RequiredInList(FieldName = "LastName", ErrorMessageResourceType = typeof(ErrorMessagesResource), ErrorMessageResourceName = "Required")]
    public List<Student> Students { get; set; }
}

where I have student as

public partial class Student
{
    public int StudentID { get; set; }

    public string LastName { get; set; }

    public string FirstMidName { get; set; }

    public System.DateTime EnrollmentDate { get; set; }

    public decimal RollNo { get; set; }
}

and my custom attribute as

[AttributeUsage(AttributeTargets.Property | AttributeTargets.Parameter, AllowMultiple = true)]
public class RequiredInListAttribute : RequiredAttribute
{
    /// <summary>
    /// Gets or sets the name.
    /// </summary>
    public string FieldName { get; set; }

    /// <summary>
    /// The is valid.
    /// </summary>
    /// <param name="value">
    /// The value.
    /// </param>
    /// <param name="validationContext">
    /// The validation context.
    /// </param>
    /// <returns>
    /// The <see cref="ValidationResult"/>.
    /// </returns>
    /// <exception cref="InvalidOperationException">
    /// Invalid operation exception
    /// </exception>
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var val = value as IEnumerable;
        if (value == null || val == null)
        {
            throw new InvalidOperationException("This attribute Required In List is intended to use only on list");
        }

        var isInvalidFiled =
            (val.Cast<object>().Select(v => v.GetType().GetProperty(this.FieldName).GetValue(v, null))).Any(
                property => property == null);

        return !isInvalidFiled
                   ? ValidationResult.Success
                   : new ValidationResult(string.Format(this.ErrorMessageString, "Last Name"), new[]{"Students[0].LastName"});
    }
}

now my problem is after posting the form, even if Last name is not provided, no error comes.

Answer 1

Put this on your CSHTML page:

 @Html.ValidationSummary()

You can also use something like this after each field in the cshtml:

  @Html.ValidationMessageFor(model => model.StudentID)