为什么我会收到InvalidCastException的铸造对象时的整数？ [英] Why am I getting InvalidCastException when casting object to integer?

问题描述

我有一个奇怪的问题，这里的设置：

I had an odd problem, here's the setup:

ASP.NET 3.5应用程序/ MSSQLSERVER 2008后端。

ASP.NET 3.5 app / MSSQLSERVER 2008 back-end.

我打电话的ExecuteScalar从我的code，它返回一个对象，然后我试图铸造的对象为int（其实我有一个通用的方法

I called ExecuteScalar from my code, which returned an object, then I tried casting that object to int (i actually have a generic method

 T ConvertDBValue<T>(object o) {...}

，但是这并不重要）。

, but that's not as important).

的ExecuteScalar打着以下存储过程：

ExecuteScalar is hitting the following sproc:

...  
insert into ...
select scope_identity()

我的主键是一个标识字段，并返回85接下来的事情我是InvalidCastException的尝试投放85为int。

My primary key is an identity field, and returned 85. Next thing I got is InvalidCastException trying to cast 85 to int.

解决方案是明确创建一个int变量，并从存储过程返回之前分配SCOPE_IDENTITY（）把它如下：

The solution was to explicitly create an INT variable, and assign SCOPE_IDENTITY() to it before returning it from the sproc as follows:

...  
DECLARE @x int
insert into ...
select @x = scope_identity()
select @x

有人可以告诉我什么是我的第一个方法的问题，为什么不把它转换85为int？

Can somebody tell me what was the problem with my first approach, and why wouldn't it cast 85 to int?

推荐答案

SCOPE_IDENTITY （） 的实际返回（TSQL） BIGINT （我被抓被在此之前！）

scope_identity() actually returns a (TSQL) BIGINT (I've been caught by this before!)

所以你的code的努力蒙上了BIGINT为int。

So your code was trying to cast a BIGINT to an int.

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