1、相差秒

public double DiffSeconds(DateTime startTime,DateTime endTime){
    TimeSpan secondSpan=new TimeSpan(endTime.Ticks-startTime.Ticks);
    return secondSpand.TotalSeconds;
}

 2、相差分钟

public double DiffMinutes(DateTime startTime,DateTime endTime){
    TimeSpan minuteSpan=new TimeSpan(endTime.Ticks-startTime.Ticks);
    return minuteSpan.TotalMinutes;
}

3、相差小时

public double DiffHours(DateTime startTime,DateTime endTime){
    TimeSpan hoursSpan=new TimeSpan(endTime.Ticks-startTime.Ticks);
    return hoursSpan.TotalHours;
}

4、相差天数

public double DiffDays(DateTime startTime,DateTime endTime){
    TimeSpan daysSpan=new TimeSpan(endTime.Ticks-startTime.Ticks);
    return daysSpan.TotalDays;
}
public int DiffDays(DateTime startTime,DateTime endTime){
    TimeSpan daysSpan=new TimeSpan(endTime.Ticks-startTime.Ticks);
    return daysSpan.Days;
}