WPF: Store XAML in Property and Display in ContentControl

问题

I am deserializing a XML file into a class and then trying to display some XAML (stored in a property in the class) in a ContentControl.

Here is my XML:

<CallSteps>
  <CallStep>
    <StepID>20</StepID>
    <StepName>Intro</StepName>
    <StepXaml>
        <![CDATA[<StackPanel xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:uc="clr-namespace:CallTracker.Library.UserControls.BaseUserControls;assembly=CallTracker.Library">
            <uc:LabelValueControl Label="TestLabel" Value="356733" />
          </StackPanel>]]>
    </StepXaml>
  </CallStep>

  <CallStep>
    <StepID>30</StepID>
    <StepName>Intro</StepName>
    <StepXaml>
        <![CDATA[<StackPanel xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                      xmlns:uc="clr-namespace:CallTracker.Library.UserControls.BaseUserControls;assembly=CallTracker.Library">
            <uc:LabelValueControl Label="TestLabel2" Value="356738124315" />
          </StackPanel>]]>
    </StepXaml>
  </CallStep>
</CallSteps>

This correctly deserializes to a collection of CallStep objects. Here is what a single CallStep object looks like:

As part of my code I have a CurrentCallStep which contains a single CallStep. I would like to display the XAML contained in StepXaml within a ContentControl (or some other container) using something like:

in VM:

/// <summary>
/// Current call step object
/// </summary>
public CallStep CurrentCallStep
{
    get { return _CurrentCallStep; }
    set
    {
        _CurrentCallStep = value;
        NotifyPropertyChanged(m => m.CurrentCallStep);
    }
}
private CallStep _CurrentCallStep;

in View:

<!-- CurrentCallStep contains the XAML for the current call steps to be displayed -->
<ContentControl Content="{Binding CurrentCallStep.StepXaml}"
                Background="LightBlue"
                HorizontalAlignment="Center"
                VerticalAlignment="Center" />

This however is not converting the XAML to XAML but rather just showing the text like:

How can I get the text in CurrentCallStep.StepXaml to convert to XAML?

回答1:

You need to use XamlServices.Load() to deserialize the string from XAML to a FrameworkElement. The property that is bounnd to should be a FrameworkElement reference, not a string reference.

回答2:

I was able to solve this by extracting the CDATA value from each StepXaml as follows:

    /// <summary>
    /// Step XAML
    /// </summary>
    [XmlElement("StepXaml")]
    public object StepXaml
    {
        get { return _StepXaml; }
        set 
        {
            if (_StepXaml != value)
            {
                object _obj;
                using (MemoryStream stream = new MemoryStream())
                {
                    // Convert the text into a byte array so that 
                    // it can be loaded into the memory stream.
                    XmlNode _node = (value as XmlNode[])[0];
                    if (_node is XmlCDataSection)
                    {
                        XmlCDataSection _cDataSection = _node as XmlCDataSection;
                        byte[] bytes = Encoding.UTF8.GetBytes(_cDataSection.Value);


                        // Write the XAML bytes into a memory stream.
                        stream.Write(bytes, 0, bytes.Length);

                        // Reset the stream's current position back 
                        // to the beginning so that when it is read 
                        // from, the read begins at the correct place.
                        stream.Position = 0;

                        // Convert the XAML into a .NET object.
                        _obj = XamlReader.Load(stream);

                        _StepXaml = _obj;
                        NotifyPropertyChanged(m => m.StepXaml);
                    }
                }
            }
        }
    }
    private object _StepXaml;

The ContentControl simply refers to the StepXaml like:

    <!-- CallContent contains the XAML for the current call steps to be displayed -->
    <ContentControl Content="{Binding CurrentCallStep.StepXaml}"

Doing it this way I didn't have to do anything special while deserializing the XML.

来源：https://stackoverflow.com/questions/28987058/wpf-store-xaml-in-property-and-display-in-contentcontrol

标签

wpf

xaml

contentcontrol