Decimal values with thousand separator in Asp.Net

问题:

I have a custom model class which contains a decimal member and a view to accept entry for this class. Everything worked well till I added javascripts to format the number inside input control. The format code format the inputted number with thousand separator ',' when focus blur.

The problem is that the decimal value inside my modal class isn't bind/parsed well with thousand separator. ModelState.IsValid returns false when I tested it with "1,000.00" but it is valid for "100.00" without any changes.

Could you share with me if you have any solution for this?

Thanks in advance.

Sample Class

public class Employee
{
    public string Name { get; set; }
    public decimal Salary { get; set; }
}

Sample Controller

public class EmployeeController : Controller
{
    [AcceptVerbs(HttpVerbs.Get)]
    public ActionResult New()
    {
        return View();
    }

    [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult New(Employee e)
    {
        if (ModelState.IsValid) // <-- It is retruning false for values with ','
        {
            //Subsequence codes if entry is valid.
            //
        }
        return View(e);
    }
}

Sample View

<% using (Html.BeginForm())
   { %>

    Name:   <%= Html.TextBox("Name")%><br />
    Salary: <%= Html.TextBox("Salary")%><br />

    <button type="submit">Save</button>

<% } %>

---

I tried a workaround with Custom ModelBinder as Alexander suggested. The probelm solved. But the solution doesn't go well with IDataErrorInfo implementation. The Salary value become null when 0 is entered because of the validation. Any suggestion, please? Do Asp.Net MVC team members come to stackoverflow? Can I get a little help from you?

Updated Code with Custom Model Binder as Alexander suggested

Model Binder

public class MyModelBinder : DefaultModelBinder {

    public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) {
        if (bindingContext == null) {
            throw new ArgumentNullException("bindingContext");
        }

        ValueProviderResult valueResult;
        bindingContext.ValueProvider.TryGetValue(bindingContext.ModelName, out valueResult);
        if (valueResult != null) {
            if (bindingContext.ModelType == typeof(decimal)) {
                decimal decimalAttempt;

                decimalAttempt = Convert.ToDecimal(valueResult.AttemptedValue);

                return decimalAttempt;
            }
        }
        return null;
    }
}

Employee Class

    public class Employee : IDataErrorInfo {

    public string Name { get; set; }
    public decimal Salary { get; set; }

    #region IDataErrorInfo Members

    public string this[string columnName] {
        get {
            switch (columnName)
            {
                case "Salary": if (Salary <= 0) return "Invalid salary amount."; break;
            }
            return string.Empty;
        }
    }

    public string Error{
        get {
            return string.Empty;
        }
    }

    #endregion
}

回答1:

It seems there are always workarounds of some form or another to be found in order to make the default model binder happy! I wonder if you could create a "pseudo" property that is used only by the model binder? (Note, this is by no means elegant. Myself, I seem to resort to similar tricks like this more and more often simply because they work and they get the job "done"...) Note also, if you were using a separate "ViewModel" (which I recommend for this), you could put this code in there, and leave your domain model nice and clean.

public class Employee
{
    private decimal _Salary;
    public string MvcSalary // yes, a string. Bind your form values to this!
    {
        get { return _Salary.ToString(); }
        set
        { 
            // (Using some pseudo-code here in this pseudo-property!)
            if (AppearsToBeValidDecimal(value)) {
                _Salary = StripCommas(value);
            }
        }
    }
    public decimal Salary
    {
        get { return _Salary; }
        set { _Salary = value; }
    }
}

P.S., after I typed this up, I look back at it now and am even hesitating to post this, it is so ugly! But if you think it might be helpful I'll let you decide...

Best of luck!
-Mike

回答2:

The reason behind it is, that in ConvertSimpleType in ValueProviderResult.cs a TypeConverter is used.

The TypeConverter for decimal does not support a thousand separator. Read here about it: http://social.msdn.microsoft.com/forums/en-US/clr/thread/1c444dac-5d08-487d-9369-666d1b21706e

I did not check yet, but at that post they even said the CultureInfo passed into TypeConverter is not used. It will always be Invariant.

           string decValue = "1,400.23";

        TypeConverter converter = TypeDescriptor.GetConverter(typeof(decimal));
        object convertedValue = converter.ConvertFrom(null /* context */, CultureInfo.InvariantCulture, decValue);

So I guess you have to use a workaround. Not nice...

回答3:

I didn't like the solutions above and came up with this:

In my custom modelbinder, I basically replace the value with the culture invariant value if it is a decimal and then hand over the rest of the work to the default model binder. The rawvalue being a array seems strange to me, but this is what I saw/stole in the original code.

        public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        if(bindingContext.ModelType == typeof(decimal) || bindingContext.ModelType==typeof(Nullable<decimal>))
        {
            ValueProviderResult valueProviderResult = bindingContext.ValueProvider[bindingContext.ModelName];
            if (valueProviderResult != null)
            {
                decimal result;
                var array = valueProviderResult.RawValue as Array;
                object value;
                if (array != null && array.Length > 0)
                {
                    value = array.GetValue(0);
                    if (decimal.TryParse(value.ToString(), out result))
                    {
                        string val = result.ToString(CultureInfo.InvariantCulture.NumberFormat);
                        array.SetValue(val, 0);
                    }
                }
            }
        }
        return base.BindModel(controllerContext, bindingContext);
    }

回答4:

Did you try to convert it to Decimal in the controller? This should do the trick:

string _val = "1,000.00"; Decimal _decVal = Convert.ToDecimal(_val); Console.WriteLine(_decVal.ToString());

回答5:

I implement custom validator, adding validity of grouping. The problem (that i solved in code below)is that parse method remove all thousands separator, so also 1,2,2 is considered valid.

Here my binder for decimal

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Web.Mvc;

namespace EA.BUTruck.ContactCenter.Model.Extensions
{
 public class DecimalModelBinder : 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
        {
            var trimmedvalue = valueResult.AttemptedValue.Trim();
            actualValue = Decimal.Parse(trimmedvalue, CultureInfo.CurrentCulture);

            string decimalSep = CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator;
            string thousandSep = CultureInfo.CurrentCulture.NumberFormat.NumberGroupSeparator;

            thousandSep = Regex.Replace(thousandSep, @"\u00A0", " "); //used for culture with non breaking space thousand separator

            if (trimmedvalue.IndexOf(thousandSep) >= 0)
            {
                //check validity of grouping thousand separator

                //remove the "decimal" part if exists
                string integerpart = trimmedvalue.Split(new string[] { decimalSep }, StringSplitOptions.None)[0];

                //recovert double value (need to replace non breaking space with space present in some cultures)
                string reconvertedvalue = Regex.Replace(((decimal)actualValue).ToString("N").Split(new string[] { decimalSep }, StringSplitOptions.None)[0], @"\u00A0", " ");
                //if are the same, it is a valid number
                if (integerpart == reconvertedvalue)
                    return actualValue;

                //if not, could be differences only in the part before first thousand separator (for example original input stirng could be +1.000,00 (example of italian culture) that is valid but different from reconverted value that is 1.000,00; so we need to make a more accurate checking to verify if input string is valid


                //check if number of thousands separators are the same
                int nThousands = integerpart.Count(x => x == thousandSep[0]);
                int nThousandsconverted = reconvertedvalue.Count(x => x == thousandSep[0]);

                if (nThousands == nThousandsconverted)
                {
                    //check if all group are of groupsize number characters (exclude the first, because could be more than 3 (because for example "+", or "0" before all the other numbers) but we checked number of separators == reconverted number separators
                    int[] groupsize = CultureInfo.CurrentCulture.NumberFormat.NumberGroupSizes;
                    bool valid = ValidateNumberGroups(integerpart, thousandSep, groupsize);
                    if (!valid)
                        throw new FormatException();

                }
                else
                    throw new FormatException();

            }


        }
        catch (FormatException e)
        {
            modelState.Errors.Add(e);
        }

        bindingContext.ModelState.Add(bindingContext.ModelName, modelState);
        return actualValue;
    }
    private bool ValidateNumberGroups(string value, string thousandSep, int[] groupsize)
    {
        string[] parts = value.Split(new string[] { thousandSep }, StringSplitOptions.None);
        for (int i = parts.Length - 1; i > 0; i--)
        {
            string part = parts[i];
            int length = part.Length;
            if (groupsize.Contains(length) == false)
            {
                return false;
            }
        }

        return true;
    }
 }
}

For decimal? nullable you need to add a little code before

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Web.Mvc;

namespace EA.BUTruck.ContactCenter.Model.Extensions
{
 public class DecimalNullableModelBinder : 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
        {
             //need this condition against non nullable decimal
             if (string.IsNullOrWhiteSpace(valueResult.AttemptedValue))
                return actualValue;
            var trimmedvalue = valueResult.AttemptedValue.Trim();
            actualValue = Decimal.Parse(trimmedvalue,CultureInfo.CurrentCulture);

            string decimalSep = CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator;
            string thousandSep = CultureInfo.CurrentCulture.NumberFormat.NumberGroupSeparator;

            thousandSep = Regex.Replace(thousandSep, @"\u00A0", " "); //used for culture with non breaking space thousand separator

            if (trimmedvalue.IndexOf(thousandSep) >=0)
            {
                //check validity of grouping thousand separator

                //remove the "decimal" part if exists
                string integerpart = trimmedvalue.Split(new string[] { decimalSep }, StringSplitOptions.None)[0];

                //recovert double value (need to replace non breaking space with space present in some cultures)
                string reconvertedvalue = Regex.Replace(((decimal)actualValue).ToString("N").Split(new string[] { decimalSep }, StringSplitOptions.None)[0], @"\u00A0", " ");
                //if are the same, it is a valid number
                if (integerpart == reconvertedvalue)
                    return actualValue;

                //if not, could be differences only in the part before first thousand separator (for example original input stirng could be +1.000,00 (example of italian culture) that is valid but different from reconverted value that is 1.000,00; so we need to make a more accurate checking to verify if input string is valid


                //check if number of thousands separators are the same
                int nThousands = integerpart.Count(x => x == thousandSep[0]);
                int nThousandsconverted = reconvertedvalue.Count(x => x == thousandSep[0]);

                if(nThousands == nThousandsconverted)
                {
                    //check if all group are of groupsize number characters (exclude the first, because could be more than 3 (because for example "+", or "0" before all the other numbers) but we checked number of separators == reconverted number separators
                    int[] groupsize = CultureInfo.CurrentCulture.NumberFormat.NumberGroupSizes;
                    bool valid = ValidateNumberGroups(integerpart, thousandSep, groupsize);
                    if (!valid)
                        throw new FormatException();

                }
                else
                    throw new FormatException();

            }


        }
        catch (FormatException e)
        {
            modelState.Errors.Add(e);
        }

        bindingContext.ModelState.Add(bindingContext.ModelName, modelState);
        return actualValue;
    }

    private bool ValidateNumberGroups(string value, string thousandSep, int[] groupsize)
    {
        string[] parts = value.Split(new string[] { thousandSep }, StringSplitOptions.None);
        for(int i = parts.Length-1; i > 0; i--)
        {
            string part = parts[i];
            int length = part.Length;
            if (groupsize.Contains(length) == false)
            {
                return false;
            }
        }

        return true;
    }
 }

}

You need to create similar binder for double, double?, float, float? (the code is the same of DecimalModelBinder and DecimalNullableModelBinder; you need just to replace type in 2 point where there is "decimal").

Then in global.asax

ModelBinders.Binders.Add(typeof(decimal), new DecimalModelBinder());
ModelBinders.Binders.Add(typeof(decimal?), new DecimalNullableModelBinder());
ModelBinders.Binders.Add(typeof(float), new FloatModelBinder());
ModelBinders.Binders.Add(typeof(float?), new FloatNullableModelBinder());
ModelBinders.Binders.Add(typeof(double), new DoubleModelBinder());
ModelBinders.Binders.Add(typeof(double?), new DoubleNullableModelBinder());

This solution works fine on server side, like the client part using jquery globalize and my fixing reported here https://github.com/globalizejs/globalize/issues/73#issuecomment-275792643

回答6:

Hey I had one more thought... This builds on Naweed's answer, but will still let you use the default model binder. The concept is to intercept the posted form, modify some of the values in it, then pass the [modified] form collection to the UpdateModel (default model binder) method... I use a modified version of this for dealing with checkboxes/booleans, to avoid the situation where anything other than "true" or "false" causes an unhandled/silent exception within the model binder.

(You would of course want to refactor this to be more re-useable, to perhaps deal with all decimals)

public ActionResult myAction(NameValueCollection nvc)
{
    Employee employee = new Employee();
    string salary = nvc.Get("Salary");
    if (AppearsToBeValidDecimal(salary)) {
        nvc.Remove("Salary");
        nvc.Add("Salary", StripCommas(salary));
    }
    if (TryUpdateModel(employee, nvc)) {
        // ...
    }
}

P.S., I may be confused on my NVC methods, but I think these will work.