从SQL Server读取十进制值时发生溢出异常 [英] Overflow exception when reading decimal values from SQL Server

问题描述

我想知道这是一个错误还是我出了什么问题。

I'm wondering whether this is a bug or if I'm going something wrong.

我正在使用 SqlDataReader加载值来自SQL Server 2008数据库，但是在某些情况下，它无法将SQL值转换为.net值。 （.NET 4.0）

I'm loading values with a SqlDataReader from a SQL Server 2008 database but under certain circumstances, it fails to convert the SQL values into .net values. (.NET 4.0)

我已将其追溯到一个演示实际问题的测试用例：

I have traced it down to an test-case which demonstrates the actual problem:

工作示例：

"select convert(decimal(38, 19), 260000 ) as test"
rs.GetValue(1);
--> returns 260000 (decimal)

不起作用的例子：

"select convert(decimal(36, 26), 260000 ) as test"

rs.GetValue(1);
--> throws
   System.OverflowException: Conversion overflows.
   at System.Data.SqlClient.SqlBuffer.get_Decimal()
   at System.Data.SqlClient.SqlBuffer.get_Value()
   at System.Data.SqlClient.SqlDataReader.GetValueInternal(Int32 i)
   at System.Data.SqlClient.SqlDataReader.GetValues(Object[] values)

I检查了SQL Server记录的实际值。它们的区别在于，不工作的人使用4个整数表示值，工作的人仅使用3个整数。

I have examined the actual values that the SQL Server retured. They differ that the non-working one uses 4 integers to express the value, the working one only 3.

我也使用.net Reflector检查了源代码如果存在的值超过3个，则会引发异常，但我不理解其背后的机制。

I did also check the source code with .net Reflector which unveiled that an exception is thrown if the value exists of more then 3 values, but I dont understand the mechanics behind them.

所以，我想知道这是否是真正的.net框架中的错误。

So, I'm wondering whether this is a genuine bug in the .net framework.

推荐答案

除了可能过于精确之外，您所做的并不是错。我不认为这是。

Its not somthing you are doing wrong, apart from being overly precise perhaps. I don't think its a new problem either.

您可能会认为它是一个错误，或者只是功能上的空白。 .Net 十进制结构只是不能表示存储在SQL Server 十进制中的值，因此<$会引发c $ c> OverflowException 。

You could argue its a bug, or just a gap in functionality. The .Net Decimal structure just can't represent the value that is stored in your SQL Server decimal so an OverflowException is thrown.

您需要在检索值之前对数据库中的兼容值进行操作，或者阅读数据以原始二进制或字符串格式输出，并在.Net端进行操作。

Either you need to manipulate the value to something compatible in the database before you retrieve it or, read the data out in a raw binary or string format and manipulate on the .Net side.

或者，您可以编写一个处理它的新类型。

Alternatively, you could write a new type that handles it.

首先使用兼容的十进制定义可能会更简单，除非您确实需要这种精度。如果您愿意，我想知道为什么。

It's probably simpler just to use a compatible decimal definition in the first place, unless you really need that precision. If you do I'd be interested to know why.

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