WPF 基础

MultiBinding 与 Binding 一样继承自 BindingBase，因此可以使用 Binding 的地方都可以使用 MultiBinding。

namespace System.Windows.Data
{
    [ContentProperty("Bindings")]
    public class MultiBinding : BindingBase, IAddChild
    {
        ...
        public Collection<BindingBase> Bindings { get; }
    }
}

例子：
在一个注册界面中，当两次输入的密码一致且邮箱不为空时，可以点击提交。

<StackPanel Grid.Row="12">
    <TextBox x:Name="passwd"/>
    <TextBox x:Name="passwdConfirm"/>
    <TextBox x:Name="email"/>
    <Button x:Name="buttonSubmit" Content="click me" Width="100" HorizontalAlignment="Left" Click="buttonSubmit_Click"/>
</StackPanel>

public class LogonMultiBindingConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        if ( !values.Cast<string>().Any(text => string.IsNullOrWhiteSpace(text))
            && values[0].ToString() == values[1].ToString() 
            && !string.IsNullOrWhiteSpace(values[2].ToString()))
        {
            return true;
        }

        return false;             
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}
    
Binding b1 = new Binding("Text") { Source = this.passwd };
Binding b2 = new Binding("Text") { Source = this.passwdConfirm };
Binding b3 = new Binding("Text") { Source = this.email };

MultiBinding mb = new MultiBinding() { Mode=BindingMode.OneWay };
mb.Bindings.Add(b1);
mb.Bindings.Add(b2);
mb.Bindings.Add(b3);
mb.Converter = new LogonMultiBindingConverter();

this.buttonSubmit.SetBinding(Button.IsEnabledProperty, mb);