如何在 WPF 中将变量作为 Converterparameter 传递

How to pass a variable as Converterparameter in WPF

提问by Vahid

I'm trying to pass a variable defined in the code behind as ConverterParameter. I'll use this parameter in the converter then to decide on some unit conversion. The problem is I don't know how to pass this. The variable is not static.

我正在尝试将在后面的代码中定义的变量作为ConverterParameter. 我将在转换器中使用此参数，然后决定某些单位转换。问题是我不知道如何通过这个。变量不是静态的。

<TextBox Text="{Binding MinimumRebarsVerticalDistance, Converter={StaticResource LengthConverter}, ConverterParameter={CurrentDisplayUnit}}"/>

Code behind:

后面的代码：

private Units currentDisplayUnit;
public Units CurrentDisplayUnit
{
    get { return currentDisplayUnit; }
    set
    {
        currentDisplayUnit = value;
        RaisePropertyChanged("CurrentDisplayUnit");
    }
}

回答by Dennis

You can use MultiBindingfor this purpose.
First, implement LengthConverteras IMultiValueConverter:

您可以MultiBinding为此目的使用。
首先，实现LengthConverter为IMultiValueConverter：

public sealed class LengthConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        // values array will contain both MinimumRebarsVerticalDistance and 
        // CurrentDisplayUnit values
        // ...
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        // ...
    }
}

Second, bind TextBox.Textwith multibinding:

二、TextBox.Text用多重绑定绑定：

        <TextBox.Text>
            <MultiBinding Converter="{StaticResource LengthConverter}">
                <Binding Path="MinimumRebarsVerticalDistance"/>
                <Binding Path="CurrentDisplayUnit" RelativeSource="{RelativeSource Mode=FindAncestor, AncestorType={x:Type Window}}"/>
            </MultiBinding>
        </TextBox.Text>

Note 1: RelativeSource.AncestorTypedepends on where CurrentDisplayUnitproperty is declared (the sample is for window's code behind).

注 1：RelativeSource.AncestorType取决于CurrentDisplayUnit声明属性的位置（示例用于窗口的代码后面）。

Note 2: looks like CurrentDisplayUnitshould be a view model property.

注 2：看起来CurrentDisplayUnit应该是一个视图模型属性。

回答by j.xavier.atero

I had a similar situation where I needed to show a double with a number of decimals based on a value set by the user. I solved it using a Singleton.

我有一个类似的情况，我需要根据用户设置的值显示一个带有多个小数的双精度数。我使用单例解决了它。

MyConfiguration.cs

我的配置文件

   public sealed class MyConfiguration
   {
      #region Singleton
      private static readonly Lazy<MyConfiguration> lazy = new Lazy<MyConfiguration>(() => new MyConfiguration());
      public static MyConfiguration Instance { get { return lazy.Value; } }
      private MyConfiguration() {}
      #endregion

      public int NumberOfDecimals { get; set; }
   }

MyConverters.cs

我的转换器.cs

   /// <summary>
   /// Formats a double for display in list
   /// </summary>
   public class DoubleConverter : IValueConverter
   {
      public object Convert(object o, Type type, object parameter, CultureInfo culture)
      {

         //--> Initializations
         IConvertible iconvertible__my_number = o as IConvertible;
         IConvertible iconvertible__number_of_decimals = parameter as IConvertible;

         //--> Read the value
         Double double__my_number = iconvertible__my_number.ToDouble(null);

         //--> Read the number of decimals       
         int number_of_decimals = MyConfiguration.Instance.NumberOfDecimals; // get configuration
         if (parameter != null)  // the value can be overwritten by specifying a Converter Parameter
         {
            number_of_decimals = iconvertible__number_of_decimals.ToInt32(null);
         }

         //--> Apply conversion
         string string__number = (Double.IsNaN(double__number)) ? "" : (number_of_decimals>=0) ? Math.Round(double__my_number, number_of_decimals).ToString(): double__my_number.ToString();

         return string__number;
      }

      public object ConvertBack(object o, Type type, object parameter, CultureInfo culture)
      {
         throw new NotSupportedException();
      }
   }

NumberOfDecimals has to be set before calling the XALM form.

NumberOfDecimals 必须在调用 XALM 表单之前设置。

MyConfiguration.Instance.NumberOfDecimals = user_defined_value;

回答by RenDishen

ConverterParameter is not a dependency property and you cant bind any variable here.

ConverterParameter 不是依赖属性，您不能在此处绑定任何变量。