强制转换异常处理程序 [英] Cast Exception Handler

问题描述

我遇到错误指定的类型转换无效

I am having an error Specified cast is not valid

//this is the code in the booking form
// time is public static
time = TimeSpan.Parse(dtpTime.Value.ToShortTimeString());
//this is the code in another form
while (rdr.Read())
{
    for (int i = 0; i < rdr.FieldCount; i++)
    {
        if ((TimeSpan)rdr[6] > Booking.time)
        {
            // etc etc
        }
    }
}

推荐答案

我假设rdr.Read()返回字符串?如果是这样，您将需要使用Timespan.Parse或Timespan.TryParse来解析字符串，您不能仅仅因为没有定义字符串的隐式或显式转换而进行强制转换.

I''m assuming rdr.Read() returns a string? If so, you will need to use Timespan.Parse or Timespan.TryParse to parse the string, you cannot just cast as there is no implicit or explicit conversion from string defined.

那是什么?项目的数据类型?
:)

So what is the data type of the item?
:)

什么是rdr?
什么是rdr [6]?
您是否看过使用调试器?在"if((TimeSpan)rdr [6]> Booking.time)"行上放置一个断点，然后查看rdr数组包含的内容.

What is rdr?
What is rdr[6]?
Have you looked using the debugger? Put a breakpoint on the "if ((TimeSpan)rdr[6] > Booking.time)" line and see what the rdr array contains.

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