PSDefaultVariablizer revisted | Brian Hartsock's Blog

A couple of days ago, I had a random post about PSDefaultVariablizer because I thought the name was funny. Well, I did some pretty hardcore refactoring of the class, and am pretty happy with the outcome. Overall, I think it is 100x better. Check it out.

public class PSDefaultVariablizer<T> where T: class
{
    T innerValue;
    IList<Func<T>> defaultValues;
 
    public PSDefaultVariablizer(params Func<T>[] _defaultValues)
    {
        defaultValues = _defaultValues.ToList();
        defaultValues.Insert(0, () => this.innerValue);
    }
 
    public T Value
    {
        get
        {
            return defaultValues.Select(v => v.Invoke())
                .Where(v => v != null)
                .FirstOrDefault();
        }
        set
        {
            innerValue = value;
        }
    }
}
 
//I am using it in a cmdlet similar to this
[Cmdlet("Some", "Command")]
public class SomeCommand : PSCmdlet
{
    private PSDefaultVariablizer<string> someParam;
 
    public SomeCommand ()
    {
        someParam = new PSDefaultVariablizer<string>(() => (string)this.SessionState.PSVariable.GetValue("SomeParam", null));
    }
 
    [Parameter()]
    public string SomeParam
    {
        get
        {
            return someParam.Value;
        }
        set
        {
            someParam.Value = value;
        }
    }
}

Thought it was cool to use Lamba’s to eliminate an entire dependency. I should really call this DefaultVariablizer because it has no dependency to Powershell.