WPF 使用MultiBinding ，TwoWay ，ValidationRule ，需要注意的事项

当wpf使用multibinding时， 其内部的validaterule的value 是其多个Binding的值， 要根据情况去验证， 还有就是在做IMultiConverter的ConvertBack时注意TargetType

如： 以下是一个Textbox通过MultiBinding绑定到后台 的字段， 以及前台的一个radiobutton, 该textbox有个validaterule。 

  < TextBox x : Name ="txtPatientWeight" TextWrapping ="Wrap" Margin ="3" MaxLength ="5" TabIndex ="6" BorderBrush ="Black" Grid.Row ="5" Grid.Column ="1" Height ="22" MinWidth ="42" Tag ="PatientWeight"

                     Visibility ="{ Binding DataContext , ElementName =window, Converter ={ StaticResource KeyToVisibilityConverter }, ConverterParameter =PatientWeight}">

                < MultiBinding   Mode ="TwoWay" Converter ="{ StaticResource WeightConverter }"    UpdateSourceTrigger ="PropertyChanged">

                    < MultiBinding.ValidationRules >

                        < McsfPAFEContainee_ValidationRules : WeightValidationRule ValidatesOnTargetUpdated ="True" ValidationStep ="ConvertedProposedValue"/>

                    </ MultiBinding.ValidationRules >

                    < Binding Path ="PatientWeight"/>

                    < Binding Path ="IsChecked" ElementName ="rdoKg"/>

                </ MultiBinding >

                < i : Interaction.Behaviors >

                    < McsfPAFEContainee_Behaviors : NumericTextBoxBehavior MinValue ="0" MaxValue ="300" />

                </ i : Interaction.Behaviors >

            </ TextBox >

////////////////////////

 <RadioButton x:Name="rdoKg" Content="kg" GroupName="WeightMeasure" d:LayoutOverrides="GridBox" MinWidth="34" Margin="5,0,0,0" Tag="PatientWeight" HorizontalAlignment="Center">

                    < RadioButton.IsChecked >

                        < Binding Path ="DataContext" Mode ="TwoWay" ElementName ="window" Converter ="{ StaticResource DefaultUnitConverter }" ConverterParameter ="kg"   UpdateSourceTrigger ="PropertyChanged"></ Binding >

                    </ RadioButton.IsChecked >

                </ RadioButton >

//////////////

   private string patientWeight = "" ; //(0010,1030) Patient Weight PatientWeight DS unit kg

        public string PatientWeight

        {

            get { return patientWeight ; }

            set

            {

                if ( value == patientWeight )

                {

                    return ;

                }

                patientWeight = value ;

                OnPropertyChanged ( "PatientWeight" );

            }

        }

  

//////////converter

  public class WeightConverter : IMultiValueConverter

    {

        public object Convert( object [] values, Type targetType, object parameter, CultureInfo culture)

        {

            if ( null == values || 2 != values.Length )

            {

                return "" ;

            }

            string unit = "" ;

            string temp = values[0].ToString();

            if ( String .IsNullOrEmpty(temp))

            {

                return "" ;

            }

            if (0 <= temp.IndexOf( "lb" ))

            {

                unit = "lb" ;

            }

            else if (0 <= temp.IndexOf( "kg" ))

            {

                unit = "kg" ;

            }

            else

            {

                return "" ;

            }

            string number = "" ;

            number = temp.Substring(0, temp.IndexOf(unit));

            //KG

            if (( bool )values[1])

            {

                measurementUnit = "kg" ;

            }

            else //LB

            {

                measurementUnit = "lb" ;

            }

            return ConvertToTargetValue(number, unit, measurementUnit);

        }

        private string measurementUnit = "" ;

      

        public object [] ConvertBack( object value, Type [] targetTypes, object parameter, CultureInfo culture)

        {

            string temp = value.ToString();

            if ( String .IsNullOrEmpty(temp))

            {

                return new object []{ DependencyProperty .UnsetValue, DependencyProperty .UnsetValue};

            }

            if ( String .IsNullOrEmpty(measurementUnit))

            {

                measurementUnit = ( PAFEContainee .MainDataContext as MainViewModel ).PRCfgVM.IsDefaultKilogram ? "kg" : "lb" ;

            }

            object [] list = new object [2];

            list[0] = value.ToString() + measurementUnit;

            list[1] = measurementUnit.Equals( "kg" ) ? "true" : "false" ;

            return list;

        }

        private string ConvertToTargetValue( string before, string beforeUnit, string afterUnit)

        {

            string result = "" ;

            if (beforeUnit.Equals(afterUnit))

            {

                return before;

            }

            switch (afterUnit)

            {

                case "lb" :

                    result = ConvertKgToPound(before).ToString();

                    break ;

                case "kg" :

                    result = ConvertPoundToKg(before).ToString();

                    break ;

                default :

                    break ;

            }

            return result;

        }

        private double ConvertPoundToKg( string pound)

        {

            double kg = 0.4536 * double .Parse(pound);

            return kg;

        }

        private double ConvertKgToPound( string kg)

        {

            double pound = 2.20 * double .Parse(kg);

            return pound;

        }

    }

///////ValidationRule

  public override ValidationResult DoValidate ( object value , CultureInfo cultureInfo )

        {

            try

            {

                //string field = value.ToString().Trim();

                string field = ( value as object [])[0]. ToString ();

                string pattern = @"^([1-9]|[1-9][0-9]|[1-5][0-9][0-9]|600)((kg)|(lb))$" ;

                Regex reg = new Regex ( pattern , RegexOptions . IgnoreCase );

                if ( field . Length <= 0 || false == reg . IsMatch ( field ))

                {

                    return new ValidationResult ( false , "Please input a number, for example '60'" );

                }

                else

                {

                    return ValidationResult . ValidResult ;

                }

            }

            catch

            {

                return new ValidationResult ( false , "Patient weight convert failed." );

            }

        }