Question

I want to create a generalized helper method for LoadFromXML loading and validation. If the XML I’m loading from is incomplete, I do want it to fail completely without throwing an exception. Currently, my code looks like this (more or less)

public override bool Load(XElement source)
{
    return new List<Func<XElement, bool>>
    {
        i => this.LoadHelper(i.Element(User.XML_Username), ref this._username, User.Failure_Username),
        i => this.LoadHelper(i.Element(User.XML_Password), ref this._password, User.Failure_Password)
        //there are many more invokations of LoadHelper to justify this architecture
    }
    .AsParallel()
    .All(i => i.Invoke(source));
}

private bool LoadHelper(XElement k, ref string index, string failure)
{
    if (k != null && k.Value != failure)
    {
        index = k.Value;
        return true;
    }
    return false;
}

this._username is a private member variable that is used by the property this.Username. This is the current solution I have for this problem, but I’m facing one major issue: Since I cannot pass the property itself to the LoadHelper and Action<string> doesn’t match the property :(, I’m circumventing the property setter logic right now.

For your own musings, before the LoadHelper abstraction, each of my List<Func<XElement, bool>>‘s entries looked like this…

i => ((Func<XElement, bool>)(k => { if (k == null || k.Value == User.Failure_Username) return false; 
                    { this.Username = k.Value; return true; } })).Invoke(i.Element(User.XML_Username)),

Question: Does anyone know any way to do this without circumventing the property’s setter logic?

Answer 1

Action doesn’t match the property

If I read that right, you tried replacing the “ref string index”, with “Action<string>” and then tried passing the Protperty. Close but not quite. How ’bout?

private bool LoadHelper(XElement k, Action<string> setter, string failure) 
{ 
    if (k != null && k.Value != failure) 
    { 
        setter(k.Value); 
        return true; 
    } 
    return false; 
} 

then

  i => this.LoadHelper(i.Element(User.XML_Username), s=>{this.Username = s},
                          User.Failure_Username),