Maintain Grid cell height and width maintain on grid move using mouse - wpf

Question

<Grid>
<Grid x:Name="thumbGrid" ShowGridLines="True" ClipToBounds="True">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="{Binding Path=ThumbSelectorLeftMargin, Mode=TwoWay}"/>
<ColumnDefinition Width="{Binding Path=ThumbWidthSelector, Mode=TwoWay}"/>
<ColumnDefinition Width="{Binding Path=ThumbSelectorRightMargin, Mode=TwoWay}" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="{Binding Path=ThumbSelectorTopMargin, Mode=TwoWay}" />
<RowDefinition Height="{Binding Path=ThumbHeightSelector, Mode=TwoWay}"/>
<RowDefinition Height="{Binding Path=ThumbSelectorBottomMargin, Mode=TwoWay}"/>
</Grid.RowDefinitions>
<GridSplitter Grid.Column="0" Grid.RowSpan="3" HorizontalAlignment="Right" BorderBrush="Transparent"
BorderThickness="2" ShowsPreview="True" DragCompleted="ThumbLeftGridSplitterDragCompleted" />
<GridSplitter Grid.Column="2" Grid.RowSpan="3" HorizontalAlignment="Left" BorderBrush="Transparent"
BorderThickness="2" ShowsPreview="True" DragCompleted="ThumbRightGridSplitterDragCompleted" />
<Grid x:Name="thumbImgGrid" MouseDown="thumbImgGrid_MouseDown" MouseMove="thumbImgGrid_MouseMove" MouseUp="thumbImgGrid_MouseUp" Grid.Row="1" Grid.Column="1">
<Border x:Name="thumbBorder">
<Image Stretch="Fill"/>
<Border.Style>
<Style TargetType="Border">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=ThumbBackgroundEntity.FillType}" Value="Color">
<Setter Property="Background" Value="{Binding Path=ThumbBackgroundEntity.BackgroundColor , Mode=TwoWay}" />
</DataTrigger>
<DataTrigger Binding="{Binding Path=ThumbBackgroundEntity.FillType}" Value="NoFill">
<Setter Property="Background" Value="{Binding Path=ThumbBackgroundEntity.BackgroundColor , Mode=TwoWay}" />
</DataTrigger>
</Style.Triggers>
</Style>
</Border.Style>
</Border>
<Border Opacity="{Binding Path=ThumbBackgroundEntity.Opacity , Mode=TwoWay}">
<Image x:Name="thumbImage" Source="{Binding Path=ThumbBackgroundEntity.BackgroundImageFullPath , Mode=TwoWay, Converter={StaticResource StringToImgConverter}}"
RenderTransformOrigin="0.5, 0.5" Stretch="Fill">
<Image.LayoutTransform>
<RotateTransform Angle="{Binding Path=ThumbBackgroundEntity.ImageAngle , Mode=TwoWay}"/>
</Image.LayoutTransform>
</Image>
<Border.Style>
<Style TargetType="Border">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=ThumbBackgroundEntity.FillType}" Value="Color">
<Setter Property="Visibility" Value="Hidden" />
</DataTrigger>
<DataTrigger Binding="{Binding Path=ThumbBackgroundEntity.FillType}" Value="NoFill">
<Setter Property="Visibility" Value="Hidden" />
</DataTrigger>
</Style.Triggers>
</Style>
</Border.Style>
</Border>
</Grid>
<GridSplitter Grid.Row="0" Grid.ColumnSpan="3" HorizontalAlignment="Stretch" VerticalAlignment="Bottom" BorderBrush="Transparent" BorderThickness="2" ShowsPreview="True"/>
<GridSplitter Grid.Row="2" Grid.ColumnSpan="3" HorizontalAlignment="Stretch" VerticalAlignment="Top" BorderBrush="Transparent" BorderThickness="2" ShowsPreview="True" />
</Grid>
</Grid>
I want to move thumbImgGrid inside grid keeping height and width constant(maintain image aspect ratio)
I did following way but i could not maintain the height and width same on move.
On mouse down i calculated top left value of thumbImgGrid
private void thumbImgGrid_MouseDown(object sender, MouseButtonEventArgs e)
{
startTopLeft = thumbImgGrid.TranslatePoint(new Point(0, 0), trackGrid);
startRightBottom = new Point(startTopLeft.X + thumbImgGrid.ActualWidth, startTopLeft.Y + thumbImgGrid.ActualHeight);
thumbImgGrid.CaptureMouse();
}
Mouse move function,here i get the current thumbGrid position and get the difference of points with old and new position and difference is added or subtracted in old value.
private void thumbImgGrid_MouseMove(object sender, MouseEventArgs e)
{
if (thumbImgGrid.IsMouseCaptured)
{
Vector offset = Point.Subtract(e.GetPosition(thumbGrid), startTopLeft);
double newLeft = startTopLeft.X + offset.X;
double NewTop = startTopLeft.Y + offset.Y;
Point newRightBottom = new Point(newLeft + thumbImgGrid.ActualWidth, newLeft+ thumbImgGrid.ActualHeight);
//thumbImgGrid.Margin = new Thickness(newLeft, NewTop, newRightBottom.X, newRightBottom.Y);
_DataSource.ThumbSelectorLeftMargin = new GridLength(newLeft, GridUnitType.Star);
//_DataSource.ThumbWidthSelector = new GridLength(thumbImgGrid.ActualWidth, GridUnitType.Star);
//_DataSource.ThumbSelectorRightMargin = new GridLength(newLeft + thumbImgGrid.ActualWidth, GridUnitType.Star);
_DataSource.ThumbSelectorTopMargin = new GridLength(NewTop, GridUnitType.Star);
//_DataSource.ThumbHeightSelector = new GridLength(thumbImgGrid.ActualHeight, GridUnitType.Star);
// _DataSource.ThumbSelectorBottomMargin = new GridLength(newLeft + thumbImgGrid.ActualHeight, GridUnitType.Star);
_DataSource.UpdateThumbDimnsionLayout();
}
}
Mouse Up Function
private void thumbImgGrid_MouseUp(object sender, MouseButtonEventArgs e)
{
thumbImgGrid.ReleaseMouseCapture();
}
I am unable to maintain the height width constant on mouse move.
Thanks in advance.