如何从命令Visual Studio Extension 2017获取IWpfTextView

using Microsoft.VisualStudio.Text.Editor;
using Microsoft.VisualStudio.Text.Editor.OptionsExtensionMethods;

IWpfTextView textView = null;
if (ServiceProvider.GlobalProvider.GetService(typeof(SVsTextManager)) is IVsTextManager textManager &&
    textManager.GetActiveView(1, null, out IVsTextView activeView) == 0)
{
    textView = activeView.GetWpfTextView();
}

string text = textView.TextSnapshot.GetText();
int caretPosition = textView.Caret.Position.BufferPosition.Position;
string selectedText = textView.Selection.SelectedSpans.FirstOrDefault()?.GetText();