Changing validation range programmatically (MVC3 ASP.NET)

Question

Let's say I have this view model:

    public class MyModel
    {
        [Range(0, 999, ErrorMessage = "Invalid quantity")]
        public int Quantity { get; set; }
    }

Now, for specific instances of this model the range of valid values will change: some may not be 0, some may not be higher than 5. The min/max values for the valid ranges are coming from the DB and can change anytime.

How do I change the min/max properties of the RangeAttribute on the fly? Or what it the best way to validate my scenario?

Answer 1

Something along the lines of this might be more what your after...

ViewModel:

public class ViewModel
{
    public DateTime MinDate {get; set;}
    public DateTime MaxDate {get; set;}

    [DynamicRange("MinDate", "MaxDate", ErrorMessage = "Value must be between {0} and {1}")]
    public DateTime Date{ get; set; }
}

Library class or elsewhere:

public class DynamicRange : ValidationAttribute, IClientValidatable
    {
        private readonly string _minPropertyName;
        private readonly string _maxPropertyName;

    public DynamicRange(string minPropName, string maxPropName)
    {
        _minPropertyName = minPropName;
        _maxPropertyName = maxPropName;
    }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var minProperty = validationContext.ObjectType.GetProperty(_minPropertyName);
        var maxProperty = validationContext.ObjectType.GetProperty(_maxPropertyName);

        if(minProperty == null)
            return new ValidationResult(string.Format("Unknown property {0}", _minPropertyName));

        if (maxProperty == null)
            return new ValidationResult(string.Format("Unknown property {0}", _maxPropertyName));

        var minValue = (int) minProperty.GetValue(validationContext.ObjectInstance, null);
        var maxValue = (int) maxProperty.GetValue(validationContext.ObjectInstance, null);

        var currentValue = (int) value;

        if (currentValue <= minValue || currentValue >= maxValue)
        {
            return new ValidationResult(string.Format(ErrorMessage, minValue, maxValue));
        }

        return null;
    }

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

        rule.ValidationParameters["minvalueproperty"] = _minPropertyName;
        rule.ValidationParameters["maxvalueproperty"] = _maxPropertyName;
        yield return rule;
    }

From: MVC unobtrusive range validation of dynamic values

Answer 2

I think your best bet might be to implement a custom model binder for your specific Model (MyModel). What you could have is something like this:

public class MyModel
{
    public int Quantity { get; set; }
} // unchanged Model

public class MyViewModel
{
    public MyModel myModel { get; set; }
    public int QuantityMin { get; set; }
    public int QuantityMax { get; set; }
}

Then you can set these values, and in your custom model binder you can compare your myModel.Quantity property to the QuantityMin and QuantityMax properties.

---

Example

Model:

public class QuantityModel
{
    public int Quantity { get; set; }
}

ViewMode:

public class QuantityViewModel
{
    public QuantityModel quantityModel { get; set; }
    public int QuantityMin { get; set; }
    public int QuantityMax { get; set; }
}

Custom Model Binder:

public class VarQuantity : IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        int MinValue = Convert.ToInt32(bindingContext.ValueProvider.GetValue("QuantityMin").AttemptedValue);
        int MaxValue = Convert.ToInt32(bindingContext.ValueProvider.GetValue("QuantityMax").AttemptedValue);
        int QuantityValue = Convert.ToInt32(bindingContext.ValueProvider.GetValue("quantityModel.Quantity").AttemptedValue);

        if (!(QuantityValue >= MinValue && QuantityValue <= MaxValue))
            bindingContext.ModelState.AddModelError("Quantity", "Quantity not between values");

        return bindingContext.Model;
    }
}

Register Custom Model Binder:

ModelBinders.Binders.Add(typeof(QuantityViewModel), new VarQuantity());

Test Controller Action Methods:

    public ActionResult Quantity()
    {
        return View();
    }

    [HttpPost]
    public string Quantity(QuantityViewModel qvm)
    {
        if (ModelState.IsValid)
            return "Valid!";
        else
            return "Invalid!";
    }

Test View Code:

@model MvcTest.Models.QuantityViewModel

<h2>Quantity</h2>

@using (Html.BeginForm())
{
    @Html.Label("Enter Your Quantity: ")
    @Html.TextBoxFor(m => m.quantityModel.Quantity)
    <br />
    @Html.Label("Quantity Minimum: ")
    @Html.TextBoxFor(m => m.QuantityMin)
    <br />
    @Html.Label("Quantity Maximum: ")
    @Html.TextBoxFor(m => m.QuantityMax)
    <br /><br />
    <input type="submit" value="Submit" />
}