wpf - 如果 XAML 中的条件

Question

是否可以通过 XAML 为 wpf 实现 if 条件，如果是，请提供 if 条件的框架以检查 xaml 中的 .net 框架版本。

我正在为 Visual Studio 2010 和 2008 共享 xaml，我想为 vs2010 执行特定的代码片段并为 vs2008 隐藏相同的代码片段

Answer 1

是的，它们被称为Triggers。有不同的类型，它们会对数据绑定的数据值的变化、触发的事件甚至用户界面控件的状态做出反应。您可以在 Code Project 上的 WPF 中的触发器帖子中找到一篇描述它们的好文章。

编辑>>>

我刚刚将您的评论添加到您的问题中，我不得不说将您问题的如此重要部分放入评论中并不是一个好主意……因此，到目前为止，大多数答案都没有回答您的实际问题。出于这个原因，我对你的问题投了反对票。

在回答您的实际问题时，不，我不相信您可以使用可以识别 Visual Studio 版本之间差异的条件 XAML。如果您告诉我们您的最终目标是什么，那么我们仍然可以提供帮助。

Answer 2

看看在您的 XAML 中使用转换器。使用转换器，您可以通过执行代码在 XAML 中做出决策。例如，这将使我的按钮在某些条件下可见：

XAML

<Button
    x:Name="btnMyButton"
    Margin="2,0"
    Command="{Binding Model.MyButtonCommand}"
    Content="My Text"
    Visibility="{Binding Model.IsShowMode, Converter={StaticResource BoolToVisibilityConverter}, ConverterParameter=False}"
/>

C# 类

public class BoolToVisibilityConverter : IValueConverter
{
    public object Convert(object value, Type targetType, 
    object parameter, CultureInfo culture)
   {
    // Do the conversion 
   }

   public object ConvertBack(object value, Type targetType, 
    object parameter, CultureInfo culture)
      {
      // UnDo conversion
  }
}

Answer 3

也许你可以看看这个http://josheinstein.com/blog/2010/06/switchconverter-a-switch-statement-for-xaml/

我还没有尝试过，但似乎这可能适合你。

编辑：

这是 SwitchConverter 的代码，因为Josh 的网站似乎已关闭 -

/// <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());
    }
}