给定轴上的所有系列都必须具有相同的数据类型—错误消息，同时在图表上显示数据

I am trying to display data from my database in MVC application using google charts. When I display "int" format it works fine, but when I want to change to for example "datetime" type I get the error message: "All series on a given axis must be of the same data type". Here is my sample database: I am trying to display data from my database in