有没有办法在XAML中创建条件绑定？
示例：
<Window x:Name="Me" DataContext="{Binding ElementName=Me}">
<TextBlock>
<TextBlock.Text>
<SelectBinding Binding="{Binding MyValue}">
<Case Value="Value1" Value="value is 1!">
<Case Value="Value2" Value="value is 2!">
<Case Value="Value3" Value="value is 3!">
</SelectBinding >
</TextBlock.Text>
</TextBlock>
</Window>
最重要的是，我想根据另一个值Binding设置一个TextBlock值，该值可以是每个案例（或案例）都发送到适当的输出/设置器的情况列表。
也许我可以在我的情况下使用DataTrigger，我只是不知道我将如何做到这一点，因为我在这里没有使用任何DataTemplate。
更新
在我的场景中，我有一个UserControl，它有几个控件。
我希望根据UserControl.DataContext数据项中的某个属性，用户控件中的其他控件应该相应地受到影响。基本上与上面的示例相同，只是每个案例都会导致Setter s。
答案 0 :(得分：9)
使用DataTrigger
（已编辑 - 原版有轻微错误）
<TextBlock>
<TextBlock.Style>
<Style>
<Style.Triggers>
<DataTrigger Binding="{Binding MyValue}" Value="Value1">
<Setter Property="TextBlock.Text" Value="value is 1!"/>
</DataTrigger>
<DataTrigger Binding="{Binding MyValue}" Value="Value2">
<Setter Property="TextBlock.Text" Value="value is 2!"/>
</DataTrigger>
<DataTrigger Binding="{Binding MyValue}" Value="Value3">
<Setter Property="TextBlock.Text" Value="value is 3!"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
答案 1 :(得分：6)
你有很多选择......
我真的认为这是一种风格/设计选择 - 以上都不是更好或更差，它们只适合不同的场景。
答案 2 :(得分：5)
尝试使用Josh编写的Switch Converter：
SwitchConverter -
XAML的“开关声明” - http://josheinstein.com/blog/index.php/2010/06/switchconverter-a-switch-statement-for-xaml/
修改
以下是SwitchConverter的代码Josh's网站似乎已关闭 -
/// <summary>
/// A converter that accepts <see cref="SwitchConverterCase"/>s and converts them to the
/// Then property of the case.
/// </summary>
[ContentProperty("Cases")]
public class SwitchConverter : IValueConverter
{
// Converter instances.
List<SwitchConverterCase> _cases;
#region Public Properties.
/// <summary>
/// Gets or sets an array of <see cref="SwitchConverterCase"/>s that this converter can use to produde values from.
/// </summary>
public List<SwitchConverterCase> Cases { get { return _cases; } set { _cases = value; } }
#endregion
#region Construction.
/// <summary>
/// Initializes a new instance of the <see cref="SwitchConverter"/> class.
/// </summary>
public SwitchConverter()
{
// Create the cases array.
_cases = new List<SwitchConverterCase>();
}
#endregion
/// <summary>
/// Converts a value.
/// </summary>
/// <param name="value">The value produced by the binding source.</param>
/// <param name="targetType">The type of the binding target property.</param>
/// <param name="parameter">The converter parameter to use.</param>
/// <param name="culture">The culture to use in the converter.</param>
/// <returns>
/// A converted value. If the method returns null, the valid null value is used.
/// </returns>
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
// This will be the results of the operation.
object results = null;
// I'm only willing to convert SwitchConverterCases in this converter and no nulls!
if (value == null) throw new ArgumentNullException("value");
// I need to find out if the case that matches this value actually exists in this converters cases collection.
if (_cases != null && _cases.Count > 0)
for (int i = 0; i < _cases.Count; i++)
{
// Get a reference to this case.
SwitchConverterCase targetCase = _cases[i];
// Check to see if the value is the cases When parameter.
if (value == targetCase || value.ToString().ToUpper() == targetCase.When.ToString().ToUpper())
{
// We've got what we want, the results can now be set to the Then property
// of the case we're on.
results = targetCase.Then;
// All done, get out of the loop.
break;
}
}
// return the results.
return results;
}
/// <summary>
/// Converts a value.
/// </summary>
/// <param name="value">The value that is produced by the binding target.</param>
/// <param name="targetType">The type to convert to.</param>
/// <param name="parameter">The converter parameter to use.</param>
/// <param name="culture">The culture to use in the converter.</param>
/// <returns>
/// A converted value. If the method returns null, the valid null value is used.
/// </returns>
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}
/// <summary>
/// Represents a case for a switch converter.
/// </summary>
[ContentProperty("Then")]
public class SwitchConverterCase
{
// case instances.
string _when;
object _then;
#region Public Properties.
/// <summary>
/// Gets or sets the condition of the case.
/// </summary>
public string When { get { return _when; } set { _when = value; } }
/// <summary>
/// Gets or sets the results of this case when run through a <see cref="SwitchConverter"/>
/// </summary>
public object Then { get { return _then; } set { _then = value; } }
#endregion
#region Construction.
/// <summary>
/// Switches the converter.
/// </summary>
public SwitchConverterCase()
{
}
/// <summary>
/// Initializes a new instance of the <see cref="SwitchConverterCase"/> class.
/// </summary>
/// <param name="when">The condition of the case.</param>
/// <param name="then">The results of this case when run through a <see cref="SwitchConverter"/>.</param>
public SwitchConverterCase(string when, object then)
{
// Hook up the instances.
this._then = then;
this._when = when;
}
#endregion
/// <summary>
/// Returns a <see cref="System.String"/> that represents this instance.
/// </summary>
/// <returns>
/// A <see cref="System.String"/> that represents this instance.
/// </returns>
public override string ToString()
{
return string.Format("When={0}; Then={1}", When.ToString(), Then.ToString());
}
}
答案 3 :(得分：0)
你可以像Dan建议的那样使用转换器......
public class MyValueConverter : IValueConverter
{
public object Convert(
object value,
Type targetType,
object parameter,
System.Globalization.CultureInfo culture)
{
string myValue = value.ToString();
string output;
switch(myValue)
{
case "Value1":
output = "Value is 1";
break;
case "Value2":
output = "Value is 2";
break;
case "Value3":
output = "Value is 3";
break;
default:
output = "Invalid Value";
break;
}
return output;
}
public object ConvertBack(
object value,
Type targetType,
object parameter,
System.Globalization.CultureInfo culture)
{
//Put reverse logic here
throw new NotImplementedException();
}
}
然后你可以在你的xaml中使用它......
<TextBlock
Text="{Binding MyValue, Converter={StaticResource MyValueConverter}}"/>
答案 4 :(得分：0)
我根据接受的答案做了一个简化的，更新的转换器。 它还允许设置字符串比较和默认大小写：
[ContentProperty("Cases")]
public class SwitchConverter : IValueConverter
{
public SwitchConverter()
{
Cases = new List<SwitchConverterCase>();
}
public List<SwitchConverterCase> Cases { get; set; }
public StringComparison StringComparisonType { get; set; } = StringComparison.InvariantCulture;
public object Default { get; set; }
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value == null || Cases == null)
{
return DependencyProperty.UnsetValue;
}
SwitchConverterCase result = Cases.FirstOrDefault(c => string.Equals(value.ToString(), c.When, StringComparisonType));
return result != null ? result.Then : Default;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
SwitchConverterCase类：
[ContentProperty("Then")]
public class SwitchConverterCase
{
public SwitchConverterCase()
{
}
public SwitchConverterCase(string when, object then)
{
When = when;
Then = then;
}
public string When { get; set; }
public object Then { get; set; }
public override string ToString() => $"When={When}; Then={Then}";
}
用法示例：
<con:SwitchConverter x:Key="StyleConverter"
Default="{x:Static FontWeights.Normal}">
<con:SwitchConverterCase When="pageHeader"
Then="{x:Static FontWeights.Bold}" />
<con:SwitchConverterCase When="header"
Then="{x:Static FontWeights.SemiBold}" />
<con:SwitchConverterCase When="smallText"
Then="{x:Static FontWeights.Light}" />
<con:SwitchConverterCase When="tinyText"
Then="{x:Static FontWeights.Thin}" />
</con:SwitchConverter>
<TextBlock FontWeight="{Binding Style, Converter={StaticResource StyleConverter}}" />
或内联：
<TextBlock>
<TextBlock.FontWeight>
<Binding Path="Style">
<Binding.Converter>
<con:SwitchConverter Default="{x:Static FontWeights.Normal}">
<con:SwitchConverterCase When="pageHeader"
Then="{x:Static FontWeights.Bold}" />
<!-- etc -->
</con:SwitchConverter>
</Binding.Converter>
</Binding>
</TextBlock.FontWeight>
</TextBlock>