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;         


        

Answer 1

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

Quantity

@using (Html.BeginForm())
{
    @Html.Label("Enter Your Quantity: ")
    @Html.TextBoxFor(m => m.quantityModel.Quantity)
    

    @Html.Label("Quantity Minimum: ")
    @Html.TextBoxFor(m => m.QuantityMin)
    

    @Html.Label("Quantity Maximum: ")
    @Html.TextBoxFor(m => m.QuantityMax)
    


    
}