// true=成功，false=失败，null=取消
private async Task <bool?> _SaveAsync()
{
bool?result = null;
if (_Saved)
{
if (File.Exists(Entrance.FileName))
{
// 当且仅当已经保存且文件存在，才认为不需要（重新）保存且保存成功
result = true;
}
// 如果文件已经保存，但不存在（被删除/移动存储介质弹出），那么重新保存
else
{
result = await AsyncMethod.SaveAsync();
// 如果保存失败，那么另存为
if (!result.Value)
{
bool?r = _SaveFileDialog.ShowDialog();
if (r ?? false)
{
result = await AsyncMethod.SaveAsAsync(_SaveFileDialog.FileName);
}
}
}
}
else
{
if (!string.IsNullOrEmpty(Entrance.FileName))
{
result = await AsyncMethod.SaveAsync();
}
// 首次保存等同于另存为
else
{
bool?r = _SaveFileDialog.ShowDialog();
if (r ?? false)
{
result = await AsyncMethod.SaveAsAsync(_SaveFileDialog.FileName);
}
}
}
_Saved = result ?? false;
return(result);
}
// true=成功，false=失败，null=取消
private async Task <bool?> _SaveAsAsync()
{
bool?result = null;
bool?r = _SaveFileDialog.ShowDialog();
if (r ?? false)
{
result = await AsyncMethod.SaveAsAsync(_SaveFileDialog.FileName);
}
_Saved = result ?? false;
return(result);
}
