将图像插入按钮时出错

将图像添加到按钮后，开始出现以下错误：

7号线（及周边）

public MainPlatform()
{
    InitializeComponent();
}

怎么修？

按钮及其属性：

<Window x:Class="-----_alpha_wpf.MainPlatform"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Background="White" Height="720" Width="1280" WindowStartupLocation="CenterScreen" WindowState="Maximized" MinWidth="1280" MinHeight="720" Title="----">
<Grid>
    <Button Content="" HorizontalAlignment="Left" Margin="10,604,0,0" VerticalAlignment="Top" Width="75" Height="76" Foreground="{x:Null}" BorderBrush="#FF006600">
        <Button.Background>
            <ImageBrush ImageSource="pack://siteoforigin:,,,/Resources/main_icon_alpha.jpg" Stretch="Uniform"/>
        </Button.Background>
    </Button>
</Grid>