出现此错误的原因是查询是在内存中执行的，而不是在RDBMS中执行. DiffMilliseconds函数是一个标记，Entity Framework提供程序将其转换为RDBMS特定的SQL以发送到RDBMS.应用于内存中的IQueryable<T>时，该函数不计算其结果，而是引发异常.

The reason you are getting this error is that the query is executed in memory, not in RDBMS. The DiffMilliseconds function is a marker that Entity Framework provider converts to RDBMS-specific SQL to send to your RDBMS. The function does not compute its result when applied to an IQueryable<T> in memory, throwing an exception instead.

如果要在内存中运行此查询，请替换

If you want to run this query in memory, replace

TotalTime = EntityFunctions.DiffMilliseconds(r.TimeStart, r.TimeEnd)

使用

TotalTime = (r.TimeEnd - r.TimeStart).TotalMilliseconds

两个日期相减会产生一个 TimeSpan 值从中可以获取其 TotalMilliseconds 属性.

Subtraction of two dates produces a TimeSpan value from which you can take its TotalMilliseconds property.