.net DataReader：指定的强制转换无效 (Int32)
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时间：2020-09-03 16:21:13 来源:igfitidea点击:
DataReader: Specified cast is not valid (Int32)
提问by moldovanu
Why does SqlDataReader throw an exception when converting 0 to integer?
为什么SqlDataReader在将0转换为整数时会抛出异常？
?dataReader(3)
0 {Short}
Short: 0
?dataReader.GetInt16(3)
0
?dataReader.GetInt32(3)
{"Specified cast is not valid."}
_HResult: -2147467262
_message: "Specified cast is not valid."
Data: {System.Collections.ListDictionaryInternal}
HelpLink: Nothing
HResult: -2147467262
InnerException: Nothing
IsTransient: False
Message: "Specified cast is not valid."
Source: "System.Data"
StackTrace: " at System.Data.SqlClient.SqlBuffer.get_Int32()
at System.Data.SqlClient.SqlDataReader.GetInt32(Int32 i)"
TargetSite: {Int32 get_Int32()}
回答by Marc Gravell
It isn't a convert - it is a cast. The same as:
这不是皈依 - 这是演员。等同于：
short x = 0;
object y = x;
int z = (int)y; // BOOM! InvalidCastException Specified cast is not valid.
In both cases, a shortis not an int.
在这两种情况下， ashort都不是int。
If unsure of the type, you might try:
如果不确定类型，您可以尝试：
int i = Convert.ToInt32(dataReader.GetValue(3));
