databinding destroy - assistance me started rudimentary example

ok... i'm vb.net winforms man perplexing know wpf the awesomeness. i'm minute simple app training experience, have reading lots information examination educational videos, nonetheless i only can't off martial rudimentary databinding, i know i'm blank simple concept. many i'd adore it, i haven't "aha!" impulse reviewing source formula yet.

so... window category i tangible tradition twine property. i blend, i try databind textbox's calm property, nonetheless ability doesn't arrangement adult brew something accessible contracting to.

can someone tell me i need supplement code/xaml below... many importantly why?

my xaml:

<window x:class="window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    title="window1" height="300" width="300">
    <grid>
        <textbox text="how i bond sometext ability here?"></textbox>
    </grid>
</window>

my window code:

class window1 

    private _sometext twine = "hello world"

    open ability sometext() string
        get
            relapse _sometext
        finish get
        set(byval value string)
            _sometext = value
        finish set
    finish property

end class