使用TSF从华宇拼音输入法获取候选词的时候，获取不到拼音分割词

[lopengye]

while (enumCompositionView.Next(1, compositionView, out fetchCount) && fetchCount > 0)
{
ITfRange range;
result = compositionView[0].GetRange(out range);
if (result)
{
var text = new char[256];
var writeCount = 0U;
//bool isEmpty;
//range.IsEmpty(ecReadOnly, out isEmpty);
range.GetText(ecReadOnly, TF_TF.TF_TF_MOVESTART, text, 255, out writeCount);
var tempStr = new string(text).Trim('\0');
resultStr += tempStr;
System.Diagnostics.Debug.WriteLine($"{tempStr}");
//OnTextOutput?.Invoke(tempStr);
//Debug.WriteLine("resultStr={0}, tempStr={1}", resultStr, tempStr);
}

                Marshal.ReleaseComObject(compositionView[0]);
            }

range.GetText(ecReadOnly, TF_TF.TF_TF_MOVESTART, text, 255, out writeCount);
这一句永远返回空字符串，求解