System.Diagnostics.Process.Start(@"文件绝对路径");

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1.xaml代码如下

在<window>中添加Loaded="Window_Loaded"

2.C#代码如下

private void Window_Loaded(object sender, RoutedEventArgs e)
{
 // 设置全屏
 this.WindowState = System.Windows.WindowState.Normal;
 this.WindowStyle = System.Windows.WindowStyle.None;
 this.ResizeMode = System.Windows.ResizeMode.NoResize;
 this.Topmost = true;
this.Left = 0.0;
 this.Top = 0.0;
 this.Width = 1600;//屏幕宽度
 this.Height = 900;//屏幕高度
 }