Button sizes become small in a stackpanel

Good Day

i have buttons and i have defined them like this

Code:

---

    <Grid>
                            <StackPanel HorizontalAlignment="Center"  VerticalAlignment="Stretch"  Orientation="Horizontal" Height="400">
                     
                            <k:KinectTileButton  Background="{x:Null}" BorderBrush="{x:Null}" Style="{x:Null}"  x:Name="btnA"    Click="btnA_Click"  MinHeight="400" MinWidth="350" Width="198"    >

                            <Image  Source="../Images/A.png"  />
                        </k:KinectTileButton>

                        <k:KinectTileButton  Background="{x:Null}" Style="{x:Null}" BorderBrush="{x:Null}"  MinHeight="400" MinWidth="350" Width="198"  x:Name="btnB"  Click="btnB_Click"    >

                            <Image  Source="/SchoolPlay1;component/Alphabets101/Images/B.png"  />
                        </k:KinectTileButton>
                        <k:KinectTileButton  Background="{x:Null}" Style="{x:Null}" BorderBrush="{x:Null}" x:Name="btnc"      Click="btnC_Click"  MinHeight="400" MinWidth="350" Width="198"      >

                            <Image  Source="/SchoolPlay1;component/Alphabets101/Images/C.png" />
                        </k:KinectTileButton>
 
                             
 
                      </StackPanel>
                        </Grid>

---

and m gridlayout has the following properties

Code:

---

  <Grid  x:Name="LayoutRoot" MinHeight="768" MinWidth="1024" >

---

and my Page does not have with and height set as i want to cater for different resolutions.


if i remove the stackPanel , my buttons bring big nicely , but i need then in a Stackpanel kind of control so that they will be aligned in order , but when i have the stack panel in the , the buttons become small, can anyone help regarding this below is the example image

Attachment 98991

Thanks