问C#关闭pdf与PdfiumViewer一起打开

EN

using (var document = PdfiumViewer.PdfDocument.Load(pdfoutputFilePath + TafCode + ".pdf"))
{
    var image = document.Render(0, 842, 595, true);  
    image.Save(imageoutputFilePath + TafCode + ".png", ImageFormat.Png);
}

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
    /// <param name="disposing">Whether this method is called from Dispose.</param>
    protected void Dispose(bool disposing)
    {
        if (!_disposed && disposing)
        {
            if (_file != null)
            {
                _file.Dispose();
                _file = null;
            }

            _disposed = true;
        }
    }