How to inject a formatted paragraph into a TextBlock?

Question

I'm trying to transmit the formatted content of a paragraph to a TextBlock, but the formatting disappears:

// Create a formatted paragraph
Paragraph para = new Paragraph();
para.FontSize = 25;
para.FontWeight = FontWeights.Bold;
para.Inlines.Add(new Run("Text of paragraph."));

// Create a span with the content of the paragraph (FontSize 25 and FontWeight Bold stay alive)
Span span = new Span(para.ContentStart, para.ContentEnd);

// Create a TextBlock with the span (FontSize 25 and FontWeight Bold get lost)
TextBlock textBlock = new TextBlock();
textBlock.Inlines.Add(span);

What could be done to keep the formatting? Thanks in advance.

Update
The formatting of the paragraph is known at runtime, so I can't apply property values one by one manually.

Update 2
The background of the question is that I want to measure the length of formatted paragraphs if they are stretched to one line. This can be done by a TextBlock. The paragraphs are located in TableCells, I want to adjust the column widths automatically.

Answer 1

I reached the following solution:

// Create a formatted Paragraph
Paragraph para = new Paragraph();
para.FontSize = 25;
para.FontWeight = FontWeights.Bold;
para.Inlines.Add(new Run("Text of paragraph."));

// Clone all Inlines
List<Inline> clonedInlines = new List<Inline>();
foreach (Inline inline in para.Inlines)
{
    Inline clonedInline = ElementClone<Inline>(inline);
    clonedInlines.Add(clonedInline);
}

// Get all Paragraph properties with a set value
List<DependencyProperty> depProps = DepPropsGet(para, PropertyFilterOptions.SetValues);

// Apply the Paragraph values to each Inline
foreach (DependencyProperty depProp in depProps)
{
    object propValue = para.GetValue(depProp);

    foreach (Inline clonedInline in clonedInlines)
    {
        // Can the Inline have the value?
        if (depProp.OwnerType.IsAssignableFrom(typeof(Inline)))
        {
            // Apply the Paragraph value
            clonedInline.SetValue(depProp, propValue);
        }
    }
}

// Create a TextBlock with the same properties as the Paragraph
TextBlock textBlock = new TextBlock();
textBlock.Inlines.AddRange(clonedInlines);

/// <summary>
/// Cloner.
/// </summary>
public static T ElementClone<T>(T element)
{
    // Element to Stream
    MemoryStream memStream = new MemoryStream();
    XamlWriter.Save(element, memStream);

    // Cloned element from Stream
    object clonedElement = null;
    if (memStream.CanRead)
    {
        memStream.Seek(0, SeekOrigin.Begin);
        clonedElement = XamlReader.Load(memStream);
        memStream.Close();
    }
    return (T)clonedElement;
}

/// <summary>
/// Property-Getter.
/// </summary>
public static List<DependencyProperty> DepPropsGet(DependencyObject depObj, PropertyFilterOptions filter)
{
    List<DependencyProperty> result = new List<DependencyProperty>();

    foreach (PropertyDescriptor pd in TypeDescriptor.GetProperties(depObj, new Attribute[] { new PropertyFilterAttribute(filter) }))
    {
        DependencyPropertyDescriptor dpd = DependencyPropertyDescriptor.FromProperty(pd);

        if (dpd != null)
        {
            result.Add(dpd.DependencyProperty);
        }
    }

    return result;
}