Default Constructor Parameter in MarkupExtension declaration

Question

Reducing this question to the bare minimum, consider this MarkupExtension class...

public class ProblemStatement : MarkupExtension
{
    private readonly string          


        

Answer 1

Try this out:

    public string Optional{ get; set; } = "DefaultValue";

    private readonly string _mandatory;

    public ProblemStatement(string mandatory)
    {
        _mandatory = mandatory;
    }

Usage:

<TextBlock Name="TextBlock1" Tag="{local:ProblemStatement 'hello', Optional=NotDefault}"/>

Alternative:

<TextBlock Name="TextBlock1" Tag="{local:ProblemStatement 'hello'}"/>

Result:

• No XAML parsing errors
• No need to overload the constructor for optional parameters
• Mandatory parameters are constructor parameters.
• Optional parameters are properties.