Increase flexibility of constructors, e.g., for pure functional transformations

Description

In the context of pure functional transformations, it would be beneficial to construct OpenXmlElement instances very flexibly. For example, one might want to construct a new element in the following way:

return new Paragraph(
    new ParagraphProperties(new ParagraphStyleId { Val = "MyStyleId" }),
    FunctionReturningIEnumerableOfRun(someParams));

Information

• .NET Target: All
• DocumentFormat.OpenXml Version: Latest

See discussion in #627.

Observed

Using the Paragraph class as an example, the subclasses of OpenXmlElement define the following constructors:

public Paragraph()
{
}

public Paragraph(IEnumerable<OpenXmlElement> childElements)
    : base(childElements)
{
}

public Paragraph(params OpenXmlElement[] childElements)
    : base(childElements)
{
}

public Paragraph(string outerXml)
    : base(outerXml)
{
}

With those constructors, the example instance can’t be created, because we can’t combine an OpenXmlElement and an IEnumerable<OpenXmlElement>.

Expected

We should be able to create instances in the way shown in the description.

Design Idea

We could borrow the design from the System.Xml.Linq.XElement class, which, owing to how you can construct instances, is instrumental in pure functional transformations.

The two key XElement constructors for pure functional transformations are:

public XElement(XName name, object content)
    : this(name)
{
    this.AddContentSkipNotify(content);
}

public XElement(XName name, params object[] content)
    : this(name, (object) content)
{
}

Note how the second constructor delegates to the first one. Thus, the magic happens in the AddContentSkipNotify(object) method, which works with pretty much any meaningful actual parameter you throw at it.

Thus, using the Paragraph example, we could replace:

• Paragraph(IEnumerable<OpenXmlElement>) with Paragraph(object) and
• Paragraph(params OpenXmlElement[]) with Paragraph(params object[]).

[ThomasBarnekow]

@twsouthwick, yes, please do that.

[ThomasBarnekow]

@twsouthwick, let me explore the extension method route. My initial thought is that this would enable the same approach while only requiring a little more code.