wpf - C# working with button when button name is in a list -

i have few button created list, need change 1 of buttons image. trying convert string button. how take string , turn in button can work ?

i have tried this:

button button = (button)this.findname("button_" + list[0].tostring()); button.background = brush;

i error of object reference not set instance of object when call button.background.

edit how have chosen change image of button:

uri resourceuri = new uri("led_on.png", urikind.relative);         streamresourceinfo streaminfo = application.getresourcestream(resourceuri);          bitmapframe temp = bitmapframe.create(streaminfo.stream);         var brush = new imagebrush();         brush.imagesource = temp;          button button = (button)findname("button_" + list[0].tostring());          button.background = brush; 

i cant grab button name button_list[0].

one possible solution change wpf button image on click event (c#) listed below:

listing 1. changing button image on click (xaml)

<button name ="button1" click="button1_click">     <button.template>         <controltemplate targettype="button">             <image x:name="image1">                 <image.style>                     <style targettype="{x:type image}">                         <setter property="source"  value="images/contentimage.png" />                     </style>                 </image.style>             </image>         </controltemplate>     </button.template> </button> 

listing 2. c# code behind (button1.click event handler)

private void button1_click(object sender, routedeventargs a) {     image _img= button1.template.findname("image1", button1) image;     style _imgstyle = new style { targettype = typeof(image) };      _imgstyle.setters.add(new setter(image.sourceproperty, new bitmapimage(new uri(@"pack://application:,,,/yourassemblyname;component//images/contentimage1.png"))));     _img.style = _imgstyle; } 

pertinent code, re-written in simple form:

streamresourceinfo _streaminfo =  application.getresourcestream(new uri("led_on.png", urikind.relative));  button.background = (new imagebrush(){imagesource=bitmapframe.create(_streaminfo.stream)}); 

just make sure button object not null (check statement: "button_" + list[0] - may list[0]?)

hope may help.