c# - C#错误: The contextual keyword 'var' may only appear within a local variable declaration

Question

我编写了以下函数来创建axWindowsMediaPlayer播放列表:

WMPLib.IWMPPlaylist p2 = axWindowsMediaPlayer.playlistCollection.newPlaylist("Playlist 1");

private void CreatePlaylist(string _currentId)
{
  string selectedElementPageTypeValue = MainContentAreaBl.GetSelectedElementPageTypeValue(_currentId);
  var selectedElementJumpToValue = MainContentAreaBl.GetSelectedElementValue(_currentId, "jumpTo");
  if (selectedElementJumpToValue != null)
  {
     _currentId = selectedElementJumpToValue;                
     if (_currentId != null && _currentId != "menu" && selectedElementPageTypeValue == "video")
     {
        var playerFile = Path.Combine(Common.ContentFolderPath, MainContentAreaBl.GetSelectedElementDataPathValue(_currentId));
        p2.appendItem(axWindowsMediaPlayer.newMedia(playerFile));
        axWindowsMediaPlayer.currentPlaylist = p2;
        CreatePlaylist(_currentId);
     }                
     axWindowsMediaPlayer.Ctlcontrols.play();
  }
}

这里var p2在类级别声明。编译应用程序时，收到以下错误消息:

The contextual keyword 'var' may only appear within a local variable declaration

但是，我无法将var p2 = axWindowsMediaPlayer.playlistCollection.newPlaylist("Playlist 1");放在递归函数中，因为它将在每次迭代时创建新的播放列表。

如何在我的函数中访问p2？

编辑1:我在“输出”窗口中看到了

COM Reference 'WMPLib' is the interop assembly for ActiveX control 'AxWMPLib' but was marked to be linked by the compiler with the /link flag. This COM reference will be treated as a reference and will not be linked.

另外，现在它在axWindowsMediaplayer上显示以下错误:

A field initializer cannot reference the non-static field, method or property

此信息与我看到的错误有什么关系吗？如何解决这个问题？

Answer 1

您将必须使用正确的类型声明它，而不是使用var:

AxWMPLib.IWMPPlaylist p2 = axWindowsMediaPlayer.playlistCollection.newPlaylist("Playlist 1");

var仅允许用于局部变量，而不能用于字段，这就是错误消息告诉您的内容。该错误消息并不意味着该字段在错误的位置声明，您只是对字段类型使用了错误的语法。