根据枚举值启用文本框 [英] Enable TextBox depending on enum value

问题描述

我有我想启用一个TextBox如果订单的状态要么是 OrderStatus.New 或 OrderStatus.Ordered 。这是其它东西，文本框应保持关闭。

I have a TextBox that I want to enable if a Order's Status is either OrderStatus.New or OrderStatus.Ordered. It it's something else, the TextBox should stay disabled.

<TextBox Text="{Binding OrderedAmount}" IsEnabled="True"/>

我想我需要使用某种MultiBinding，但似乎无法找到如何做，在这种特殊情况下适当的资源。

I assume I need to use some kind of MultiBinding, but cannot seem to find a proper resource on how to do that in this particular case.

推荐答案

您应该使用ValueConverter为此：

You should use a ValueConverter for this:

public class IsNewOrOrderedConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        OrderStatus status = (OrderStatus)value;
        return status == OrderStatus.New || status == OrderStatus.Ordered;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

然后用它作为你的XAML转换器：

Then use it as the converter in your xaml:

<TextBox Text="{Binding OrderedAmount}" 
          IsEnabled="{Binding OrderStatus, Converter={StaticResource IsNewOrOrderedConverter}"/>

不要忘了申报资源：

Don't forget to declare the resource:

 <App.Resources>
    <myPrefix:IsNewOrOrderedConverter x:Key="IsNewOrOrderedConverter" />
 </App.Resources>

http://msdn.microsoft.com/en-us/library/ ms750613.aspx 上宣布的资源。

参数化

一个单一的转换器可进行参数化，因此它可以为不同的订单类型被重用。
该XAML会是这样：

A single converter can be made parametrized so it can be reused for different order types. The XAML would be like this:

        <local:OrderStatusToBooleanConverter 
               StatusList="New,Ordered"  x:Key="NewOrOrderedConverter" />
        <local:OrderStatusToBooleanConverter 
               StatusList="Delivered"  x:Key="DeliveredConverter" />

这需要一些特殊的战术，因为没有办法在默认情况下，使其可读的（用逗号隔开的枚举值）。这就是我们需要一个类型转换器：

This requires some special tactics since there is no way by default to make it readable (with enum values separated by a comma). That's where we need a type converter:

public class StringToOrderStatusArrayConverter : TypeConverter
{
    public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
    {
        return sourceType == typeof(string);
    }
    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
    {
        if (value == null)
        {
            return new OrderStatus[0];
        }
        else
        {
            return (from s in value.ToString().Split(',')
                    select Enum.Parse(typeof(OrderStatus), s))
                    .OfType<OrderStatus>()
                    .ToArray<OrderStatus>();

        }
    }
}

类型转换器由逗号分隔成数组枚举值的输入字符串数组转换。

The type converter converts the input string array of enum values separated by a comma into an array.

这阵列可以被送入 ValueConverter ：

public class OrderStatusToBooleanConverter : IValueConverter
{
    [TypeConverter(typeof(StringToOrderStatusArrayConverter))]
    public OrderStatus[] StatusList { get; set; }

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        OrderStatus status = (OrderStatus)value;
        return StatusList != null && StatusList.Contains(status);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

这篇关于根据枚举值启用文本框的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！