ASP.NET mvc 5, Entity Framework,exclude modeldata

Question

I'm new to ASP.NET MVC and ran into a newbie question.

I've created a form where some data should only be sent from the view to the control if some conditions are met. Like, for example I got a checkbox with a text saying "today", if its unclicked a text field should appear where the user can enter a earlier date.

My question is: how do I with best practice (I've already solved it with javascript, filling/clearing the field, but that's really ugly) tell it to exclude/include the field depending on some condition.

I tried something like this:

public ActionResult Create([Bind(Include = "EventID,ActivityID", Exclude = "EventDate")] FSEvent fsevent)
{
        if (ModelState.IsValid)
        {
            if (fsevent.EventDate == DateTime.MinValue)
            {
                fsevent.EventDate = DateTime.Now;
            }

            db.FSEvents.Add(fsevent);
            db.SaveChanges();

            return RedirectToAction(returnUrl);
        }

        ViewBag.ActivityID = new SelectList(db.FSEventItems, "ActivityID", "Name", fsevent.ActivityID);
        ViewBag.UserID = new SelectList(db.FSUsers, "UserID", "FirstName", fsevent.UserID);

        return View(fsevent);
    }

But the browser gives me (the user) the error message "The EventDate field is required" with MVC EF buit in javascript validation (so if I disable the javascript it works fine).

pas · Accepted Answer · 2014-03-01 12:51:46Z

I got a similar problem and solved it using a custom attribute.
Below you can find the ViewModel, the View and the Attribute.

The ViewModel

public class TheViewModel{

    [Display(Name = "YourOtherFieldDisplayName", ResourceType = typeof(YourResourceFile))]
    public string YourOtherField { get; set; }

    [Display(Name = "YourFieldDisplayName", ResourceType = typeof(YourResourceFile))]
    [RequiredIf("TheOtherField", true, ErrorMessageResourceName = "FieldRequired", ErrorMessageResourceType = typeof(YourResourceFile))]
    public string YourField { get; set; }
}

The View

@Html.LabelFor(model => model.YourOtherField)
@Html.CheckBoxFor(model => model.YourOtherField)
@Html.LabelFor(model => model.YourField)
@Html.TextBoxFor(model => model.YourField)
@Html.ValidationMessageFor(model => model.YourField)

The Attribute

namespace YOURNAMESPACE.attributes
{
    public class RequiredIfAttribute : ValidationAttribute, IClientValidatable
    {
        private RequiredAttribute _innerAttribute = new RequiredAttribute();

        public string DependentProperty { get; set; }
        public object TargetValue { get; set; }

        public RequiredIfAttribute(string dependentProperty, object targetValue)
        {
            this.DependentProperty = dependentProperty;
            this.TargetValue = targetValue;
        }

        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            var containerType = validationContext.ObjectInstance.GetType();
            var field = containerType.GetProperty(this.DependentProperty);

            if (field != null)
            {
                var dependentvalue = field.GetValue(validationContext.ObjectInstance, null);

                // compare the value against the target value
                if ((dependentvalue == null && this.TargetValue == null) ||
                    (dependentvalue != null && dependentvalue.Equals(this.TargetValue)))
                {
                    if (!_innerAttribute.IsValid(value))
                        return new ValidationResult(this.ErrorMessage, new[] { validationContext.MemberName });
                }
            }

            return ValidationResult.Success;
        }

        public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
        {
            var rule = new ModelClientValidationRule()
            {
                ErrorMessage = FormatErrorMessage(metadata.GetDisplayName()),
                ValidationType = "requiredif",
            };

            string depProp = BuildDependentPropertyId(metadata, context as ViewContext);

            string targetValue = (this.TargetValue ?? "").ToString();
            if (this.TargetValue.GetType() == typeof(bool))
                targetValue = targetValue.ToLower();

            rule.ValidationParameters.Add("dependentproperty", depProp);
            rule.ValidationParameters.Add("targetvalue", targetValue);

            yield return rule;
        }

        private string BuildDependentPropertyId(ModelMetadata metadata, ViewContext viewContext)
        {
            // build the ID of the property
            string depProp = viewContext.ViewData.TemplateInfo.GetFullHtmlFieldId(this.DependentProperty);
            var thisField = metadata.PropertyName + "_";
            if (depProp.StartsWith(thisField))
                depProp = depProp.Substring(thisField.Length);
            return depProp;
        }
    }
}

I hope this can help you

Yishai Galatzer · Accepted Answer · 2014-03-01 17:06:53Z

0

You can also just get the data just from the field where you enter the date at, and only validate that field.

This way the checkbox where you say checked/unchecked is just helping the UI show hide stuff, but it's not part of your validation or payload. You always just get the date back from a hidden or visible field.

It will also simplify your controller code.

answered Mar 1, 2014 at 17:06

Yishai Galatzer

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