WPF中利用数据多条件触发器控制Button控件的可用性

前言
假设我们有两个文本框，需要输入姓名和年龄，且两项为必须输入的字段。这时候我们可以利用Validation类扩展自己的数据验证，同时将验证结果绑定到Button的IsEnabled属性上，当两个TextBox输入的值通过数据验证后，Button才可用。

首先，我们创建两个数据验证类

public class NameValidationRule : ValidationRule
    {
        public override ValidationResult Validate(object value, CultureInfo cultureInfo)
        {
            if (value == null || value.ToString().Length == 0)
            {
                return new ValidationResult(false, "姓名不能为空");
            }
            else
            {
                return new ValidationResult(true, null);
            }
        }    
    }
    
public override ValidationResult Validate(object value, CultureInfo cultureInfo)
        {
            if (double.TryParse(value.ToString(), out double myValue))
            {
                if (myValue >= 0 && myValue <= 100)
                {
                    return new ValidationResult(true, null);
                }
            }

            return new ValidationResult(false, "请输入 0 至 100的数字");
        }

然后我们编写前端代码

<Grid>
        <Grid Margin="50">
            <Grid.RowDefinitions>
                <RowDefinition/>
                <RowDefinition/>
                <RowDefinition/>
                <RowDefinition/>
            </Grid.RowDefinitions>
            <StackPanel Grid.Row="0" Orientation="Horizontal" HorizontalAlignment="Center">
                <TextBlock Text="姓名:" VerticalAlignment="Center"/>
                <TextBox x:Name="textBoxName" Width="200" Height="30" VerticalContentAlignment="Center">
                    <TextBox.Style>
                        <Style TargetType="TextBox">
                            <Style.Triggers>
                                <Trigger Property="Validation.HasError" Value="True">
                                    <Setter Property="ToolTip" Value="{Binding (Validation.Errors).CurrentItem.ErrorContent,RelativeSource={RelativeSource Mode=Self}}"/>
                                </Trigger>
                            </Style.Triggers>
                        </Style>
                    </TextBox.Style>
                    <TextBox.Text>
                        <Binding Path="Name" UpdateSourceTrigger="PropertyChanged">
                            <Binding.ValidationRules>
                                <validation:NameValidationRule ValidatesOnTargetUpdated="True"/>
                            </Binding.ValidationRules>
                        </Binding>
                    </TextBox.Text>
                    <Validation.ErrorTemplate>
                        <ControlTemplate>
                            <DockPanel>
                                <AdornedElementPlaceholder>
                                    <Border BorderBrush="Red" BorderThickness="1">
                                        <TextBlock HorizontalAlignment="Right" Foreground="LightGray" Background="Transparent"  Text="{Binding ErrorContent}"  VerticalAlignment="Center" Margin=" 10 0 10 0" />
                                    </Border>
                                </AdornedElementPlaceholder>
                            </DockPanel>
                        </ControlTemplate>
                    </Validation.ErrorTemplate>
                </TextBox>
            </StackPanel>
            <StackPanel Grid.Row="1" Orientation="Horizontal" HorizontalAlignment="Center">
                <TextBlock Text="年龄:" VerticalAlignment="Center"/>
                <TextBox x:Name="textBoxAge"  Width="200" Height="30" VerticalContentAlignment="Center">
                    <TextBox.Style>
                        <Style TargetType="TextBox">
                            <Style.Triggers>
                                <Trigger Property="Validation.HasError" Value="True">
                                    <Setter Property="ToolTip" Value="{Binding (Validation.Errors).CurrentItem.ErrorContent,RelativeSource={RelativeSource Mode=Self}}"/>
                                </Trigger>
                            </Style.Triggers>
                        </Style>
                    </TextBox.Style>
                    <TextBox.Text>
                        <Binding Path="Age" UpdateSourceTrigger="PropertyChanged">
                            <Binding.ValidationRules>
                                <validation:AgeValidationRule ValidatesOnTargetUpdated="True"/>
                            </Binding.ValidationRules>
                        </Binding>
                    </TextBox.Text>
                    <Validation.ErrorTemplate>
                        <ControlTemplate>
                            <DockPanel>
                                <AdornedElementPlaceholder>
                                    <Border BorderBrush="Red" BorderThickness="1">
                                        <TextBlock HorizontalAlignment="Right" Foreground="LightGray"  Text="{Binding ErrorContent}"  VerticalAlignment="Center" Margin=" 10 0 10 0" />
                                    </Border>
                                </AdornedElementPlaceholder>
                            </DockPanel>
                        </ControlTemplate>
                    </Validation.ErrorTemplate>
                </TextBox>
            </StackPanel>
            <StackPanel Grid.Row="2">
                <Button Content="提  交" Width="80" Height="30">
                    <Button.Style>
                        <Style TargetType="Button">
                            <Setter Property="IsEnabled" Value="False"/>
                            <Style.Triggers>
                                <MultiDataTrigger>
                                    <MultiDataTrigger.Conditions>
                                        <Condition Binding="{Binding ElementName=textBoxName,Path=(Validation.HasError)}" Value="False"/>
                                        <Condition Binding="{Binding ElementName=textBoxAge,Path=(Validation.HasError)}" Value="False"/>
                                    </MultiDataTrigger.Conditions>
                                    <MultiDataTrigger.Setters>
                                        <Setter Property="IsEnabled" Value="True"/>
                                    </MultiDataTrigger.Setters>
                                </MultiDataTrigger>
                            </Style.Triggers>
                        </Style>
                    </Button.Style>
                </Button>
            </StackPanel>
        </Grid>
    </Grid>

注意我们的Name和Age两个字段位于ViewModel当中

public class ValidationWindowViewModel : ViewModelBase
    {
        private int age;

        public int Age
        {
            get { return age; }
            set { age = value; RaisePropertyChanged(); }
        }

        private string  name;

        public string Name
        {
            get { return name; }
            set { name = value; RaisePropertyChanged(); }
        }

    }

这样就实现了数据验证和提交按钮绑定的要求。如下图：

由于只输入了张三，没有年龄，所以按钮是灰色

输入姓名和年龄，通过验证，按钮可用

最后

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