回答它以将其从未答复的列表中删除.

正如OP所说:
我发现这是一个项目设置问题.我将代码放在另一个项目中，并且可以正常工作.

Answering it to remove it from unanswered list.

As OP said:
I figured out that it was a project setting issue. I put the code inside another project and it worked.