How do you use the invoke method on a parameter value change?

The better solution is to invoke the method in the set value of the parameter.

@code {

    string _myString;
    [Parameter]
    public string MyString
    {
        get {return _myString; }
        set {
            _myString = value;
            this.ValueChange();
        }

    }

    private void ValueChange()
    {
        Console.WriteLine("Parameter value has changed");
    }
}

You can also override the OnParameterSet or OnParameterSetAsync lifecycle methods. Those methods are triggered every time any parameter value changes.

@code
{
    [Parameter]
    protected string MyString {get;set;}

    protected override void OnParametersSet()
    {
        this.ValueChange();
    }
    private void ValueChange()
    {
        Console.WriteLine("Parameter value has changed");
    }
}