xaml - WPF align items in container -

so have thi simple xaml:

    <textbox grid.row="0" grid.column="1" margin="10,14,10,5" borderbrush="magenta" borderthickness="1" >         <textbox.text >             <binding path="name" notifyontargetupdated="true" updatesourcetrigger="propertychanged" >                 <binding.validationrules>                     <dataerrorvalidationrule validatesontargetupdated="false"  />                 </binding.validationrules>             </binding>         </textbox.text>     </textbox>      <border grid.row="1" grid.column="1" borderthickness="1" borderbrush="lime" margin="10, 0, 10, 0">         <dockpanel  margin="0"  >             <button  margin="0, 0, 5, 0" width="100" content="first" />             <button  dockpanel.dock="right" width="100" content="second" />         </dockpanel>     </border> 

it looks so:

i place buttons such way first button left-aligned , secoond button right-aligned. can see there space between second button , right side of border. how kill off space? thank in advance!

it's because lastchildfill (of dockpanel) true default causing behavior. can set false solve problem:

<dockpanel  margin="0" lastchildfill="false">         <button  margin="0, 0, 5, 0" width="100" content="first" />         <button  dockpanel.dock="right" width="100" content="second" /> </dockpanel>