User44/NewPriority.xaml

<Window x:Class="User44.NewPriority"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:User44"
        mc:Ignorable="d"
        Title="Изменение приоритетности" Height="150" Width="250">
    <Grid>
        <StackPanel VerticalAlignment="Center">
            <TextBlock HorizontalAlignment="Center">Укажите новую приоритетность</TextBlock>
            <TextBox Name="TbValue" Width="100" Margin="0,7"></TextBox>
            <Button  Name="ButtOk" Width="60" Click="ButtOk_Click">Сохранить</Button>
        </StackPanel>
    </Grid>
</Window>