ASP.NET MVC绑定十进制值

Question

我试图弄清楚为什么框架拒绝将"1,234.00"值绑定到十进制.它可能是什么原因？

像"123.00"或"123.0000"这样的值绑定成功.

我有以下代码在Global.asax中设置我的文化配置

    public void Application_AcquireRequestState(object sender, EventArgs e)
    {
        var culture = (CultureInfo)Thread.CurrentThread.CurrentCulture.Clone();
        culture.NumberFormat.NumberDecimalSeparator = culture.NumberFormat.CurrencyDecimalSeparator = culture.NumberFormat.PercentDecimalSeparator = ".";
        culture.NumberFormat.NumberGroupSeparator = culture.NumberFormat.CurrencyGroupSeparator = culture.NumberFormat.PercentGroupSeparator = ",";
        Thread.CurrentThread.CurrentCulture = culture;
    }

法国文化在Web.Config中被设置为默认文化

  <globalization uiCulture="fr-FR" culture="fr-FR" />

我潜入了System.Web.Mvc.dll的ValueProviderResult类的源代码.它使用的是System.ComponentModel.DecimalConverter.

converter.ConvertFrom((ITypeDescriptorContext) null, culture, value)

这是消息"1,234.0000不是十进制的有效值".来自.

我试图在我的操场上运行以下代码:

static void Main()
{
    var decConverter = TypeDescriptor.GetConverter(typeof(decimal));
    var culture = new CultureInfo("fr-FR");
    culture.NumberFormat.NumberDecimalSeparator = culture.NumberFormat.CurrencyDecimalSeparator = culture.NumberFormat.PercentDecimalSeparator = ".";
    culture.NumberFormat.NumberGroupSeparator = culture.NumberFormat.CurrencyGroupSeparator = culture.NumberFormat.PercentGroupSeparator = ",";
    Thread.CurrentThread.CurrentCulture = culture;
    var d1 = Decimal.Parse("1,232.000");
    Console.Write("{0}", d1);  // prints  1234.000     
    var d2 = decConverter.ConvertFrom((ITypeDescriptorContext)null, culture, "1,232.000"); // throws "1,234.0000 is not a valid value for Decimal."
    Console.Write("{0}", d2);
}

DecimalConverter抛出相同的异常.Decimal.Parse正确解析相同的字符串.

Answer 1

问题是,它在调用时DecimalConverter.ConvertFrom不支持枚举的AllowThousands标志.好消息是,有一种方法可以"教导"它这样做!NumberStylesNumber.Parse

Decimal.Parse内部调用Number.Parse设置为的数字样式Number,AllowThousands标志设置为true.

[__DynamicallyInvokable]
public static decimal Parse(string s)
{
    return Number.ParseDecimal(s, NumberStyles.Number, NumberFormatInfo.CurrentInfo);
}

当您从描述符接收类型转换器时,您实际上获得了一个实例DecimalConverter.这种ConvertFrom方法有点普遍而且很大,所以我只引用当前场景的相关部分.缺少的部分正在实现对十六进制字符串和异常处理的支持.¹

public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
{
    if (value is string) 
    {
        // ...

        string text = ((string)value).Trim();

        if (culture == null) 
            culture = CultureInfo.CurrentCulture;

        NumberFormatInfo formatInfo = (NumberFormatInfo)culture.GetFormat(typeof(NumberFormatInfo));
        return FromString(text, formatInfo);

        // ...
    }

    return base.ConvertFrom(context, culture, value);
}

DecimalConverter也覆盖了FromString实现,问题就出现了:

internal override object FromString(string value, NumberFormatInfo formatInfo) 
{
    return Decimal.Parse(value, NumberStyles.Float, formatInfo);
}

数字样式设置为Float,AllowThousands标志设置为false!但是,您可以使用几行代码编写自定义转换器来修复此问题.

class NumericDecimalConverter : DecimalConverter
{
    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
    {
        if (value is string)
        {
            string text = ((string)value).Trim();

            if (culture == null) 
                culture = CultureInfo.CurrentCulture;

            NumberFormatInfo formatInfo = (NumberFormatInfo)culture.GetFormat(typeof(NumberFormatInfo));
            return Decimal.Parse(text, NumberStyles.Number, formatInfo);
        }
        else
        {
            return base.ConvertFrom(value);
        }
    }
}

^{1 _{请注意,代码看起来与原始实现类似.如果您需要"未加引号"的东西,可以将其直接委托给base您自己实施.您可以使用ILSpy/DotPeek/etc查看实现.或者从Visual Studio调试它们.}}

最后,在Reflection的帮助下,您可以设置类型转换器Decimal以使用新的自定义转换器!

TypeDescriptor.AddAttributes(typeof(decimal), new TypeConverterAttribute(typeof(NumericDecimalConverter)));