WPF 后台触发 Validate UI‘s Element

wpf中有validateRule类， 用于界面元素的验证， 如何后台去控制validateRule呢？

1. UI层要binding写好的ValidateRule，分为Binding和MultiBinding， 如下面分别实现了Combobox的SelectedValuePropperty的Binding

     和TextBox的TextProperty的MultiBinding。其中都有ValidationRule。

       <ComboBox x:Name="cmbAgeType" Margin="3"

                      SelectionChanged="cmbAgeType_SelectionChanged"  Background="#00000000" BorderBrush="Black" Grid.Row="4" MinWidth="0" Grid.Column="2" IsTabStop="False" SelectedIndex="0" d:LayoutOverrides="GridBox" Tag="PatientAge"

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

                <ComboBox.SelectedValue>

                    <Binding Path="PatientAge" Converter="{StaticResource AgeMeasureConverter}" Mode="TwoWay"  UpdateSourceTrigger="PropertyChanged">

                        <Binding.ValidationRules>

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

                        </Binding.ValidationRules>

                    </Binding>

                </ComboBox.SelectedValue>

                <!--<Binding Path="PatientAge" Converter=""  UpdateSourceTrigger="PropertyChanged"/>-->

            </ComboBox>

    

            <TextBox x:Name="txtPatientWeight" TextWrapping="Wrap" Margin="3" MaxLength="10" 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}">

                <TextBox.Text>

                    <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>

                </TextBox.Text>

                <i:Interaction.Behaviors>

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

                </i:Interaction.Behaviors>

            </TextBox>

2.  后台主动触发ValidationRule的验证。 以下方法根据上面的Binding， 分别去取Binding和MultiBinding， 然后调用UpdateSource。

            private bool ValidateInput(object child, PRCfgViewModel vm, bool isUpdateSource, bool isEmergency)

        {

            BindingExpression be = null;

            MultiBindingExpression mbe = null;

            if (child is TextBox)

            {

                be = (child as TextBox).GetBindingExpression(TextBox.TextProperty);

                if (null == be)

                {

                    mbe = BindingOperations.GetMultiBindingExpression((child as TextBox), TextBox.TextProperty);

                }

            }

            else if (child is DatePicker)

            {

                be = (child as DatePicker).GetBindingExpression(DatePicker.TextProperty);

                if (null == be)

                {

                    mbe = BindingOperations.GetMultiBindingExpression((child as DatePicker), DatePicker.TextProperty);

                }

            }

            else if (child is ComboBox)

            {

                be = (child as ComboBox).GetBindingExpression(ComboBox.SelectedValueProperty);

                if (null == be)

                {

                    mbe = BindingOperations.GetMultiBindingExpression((child as ComboBox), ComboBox.SelectedValueProperty);

                }

            }

            if (null == be && null == mbe)

            {

                return false;

            }

            ValidationRule vr = null;

            if (null != be && be.ParentBinding.ValidationRules.Count > 0)

            {

                vr = be.ParentBinding.ValidationRules[0];

            }

            else if (null != mbe && mbe.ParentMultiBinding.ValidationRules.Count > 0)

            {

                vr = mbe.ParentMultiBinding.ValidationRules[0];

            }

            else

            {

                return false;

            }

            string bindingPath = "";

            if (null != be)

            {

                bindingPath = be.ParentBinding.Path.Path;

            }

            else if (null != mbe)

            {

                Binding bd = mbe.ParentMultiBinding.Bindings[0] as Binding;

                bindingPath = bd.Path.Path;

            }

            bindingPath = bindingPath.Replace(".", "_");

            if (vm.Setting.CfgInfo[bindingPath] != null)

            {

                (vr as BaseValidationRule).IsActive = !isEmergency;

                if ((vr as BaseValidationRule).IsActive)

                {

                    (vr as BaseValidationRule).IsAllowEmpty = !(vm.Setting.CfgInfo[bindingPath].IsKeyword);

                }

                else

                {

                    if (isUpdateSource)

                    {

                        if (null != be)

                        {

                            be.UpdateSource();

                        }

                        else if (null != mbe)

                        {

                            mbe.UpdateSource();

                        }

                    }

                    return true;

                }

            }

            else

            {

                (vr as BaseValidationRule).IsAllowEmpty = true;

            }

            if (isUpdateSource)

            {

                if (null != be)

                {

                    be.UpdateSource();

                }

                else if (null != mbe)

                {

                    mbe.UpdateSource();

                }

            }

            return true;

        }