CommentPostPanel.xaml

<UserControl x:Class="PeriscopeSitePlugin.CommentPostPanel"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:PeriscopeSitePlugin"
             d:DataContext="{d:DesignInstance local:CommentPostPanelViewModel, IsDesignTimeCreatable=True}"
             mc:Ignorable="d" Height="50" Width="330">
    <Grid Margin="0">
        <TextBox HorizontalAlignment="Stretch" Height="23" IsEnabled="{Binding CanPostComment}" Margin="0,27,85,0" TextWrapping="NoWrap" Text="{Binding Comment}" VerticalAlignment="Bottom" />
        <Button Content="投稿" Command="{Binding PostCommentCommand}" IsEnabled="{Binding CanPostComment}" HorizontalAlignment="Right" Margin="0,27,0,0" VerticalAlignment="Bottom" Width="75"/>

    </Grid>
</UserControl>