asp.net mvc validation annotation for dollar currency - asp.net

Question

I am validation for Html.TextBoxFor. Here is my code on the view
#Html.TextBoxFor(m => m.Amount, new {#class = "form-control", Value = String.Format("{0:C}", Model.Amount) })
This code takes the double value from the database like 5000.00 and displays on the UI as $5,000.00. However when the user hits the submit button, a validation error is displayed that
The value '$5,000.00' is not valid for Amount.
My validation annotation on the Model is
[Range(0, double.MaxValue, ErrorMessage = "Please enter valid dollar amount")]
To get it to submit, I had to retype as 5000.00. How can I fix this? Thanks.

Answer 1

When you do the value = string.Format("{0:C}", Model.Amount) in the htmlAttributes, razor will execute the C# code and return the value,"$125.67", (Assuming the value of your Amount property is 125.67M) which is a string. So the markup generated by your view will be
<input value="$125.67" class="form-control" id="Amount" name="Amount" type="text">
Now since $125.67 is not not a valide decimal value, but a string. it cannot map the value of this textbox to the Amount property of your view model which is of type decimal/doube.
What you can do is, create a new property in your view model of type string to store this formatted string value and when user submits the form, try to parse it back to a decimal variable and use it.
So add a new property to your view model
public class CreateOrderVm
{
public int Id { set;get;}
public string AmountFormatted { set;get;} // New property
public decimal Amount { set;get;}
}
And in your view, which is strongly typed to CreateOrderVm
#model CreateOrderVm
#using(Html.BeginForm())
{
#Html.TextBoxFor(m => m.AmountFormatted, new { #class = "form-control",
Value = String.Format("{0:C}", Model.Amount) })
<input type="submit" />
}
And in your HttpPost action
[HttpPost]
public ActionResult Create(CreateOrderVm model)
{
decimal amountVal;
if (Decimal.TryParse(vm.AmountFormatted, NumberStyles.Currency,
CultureInfo.CurrentCulture, out amountVal))
{
vm.Amount = amountVal;
}
else
{
//add a Model state error and return the model to view,
}
//vm.Amount has the correct decimal value now. Use it to save
// to do :Return something
}

Answer 2

You can create you own Binder object to handle this. First create this object:
public class DoubleModelBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
ValueProviderResult valueResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
ModelState modelState = new ModelState { Value = valueResult };
object actualValue = null;
try
{
if (!string.IsNullOrEmpty(valueResult.AttemptedValue))
actualValue = Convert.ToDouble(valueResult.AttemptedValue.Replace("$", ""), System.Globalization.CultureInfo.CurrentCulture);
}
catch (FormatException e)
{
modelState.Errors.Add(e);
}
if (bindingContext.ModelState.ContainsKey(bindingContext.ModelName))
bindingContext.ModelState[bindingContext.ModelName] = modelState;
else
bindingContext.ModelState.Add(bindingContext.ModelName, modelState);
return actualValue;
}
}
Then in your Global.asax.cs file in the Application_Start function, add this:
ModelBinders.Binders.Add(typeof(double?), new DoubleModelBinder());