INSERT INTO Customers (
         Type,Name,Address,ContactName,ContactNumber,ContactEmail,Supplier)
VALUES (
         @Type,@Name,@Address,@ContactName,@ContactNumber,@ContactEmail,@Supplier)

SELECT @@IDENTITY

对connection.Query< int>(sql,…)的调用抛出了无效的强制转换异常.我调试了它,它是在Dapper在返回的sqlDataReader上调用GetValue的时候.

返回类型GetValue是Object,在调试器show中检查它是一个盒装小数.

如果我将select更改为SELECT CAST(@@ IDENTITY as int),则GetValue的返回值为Boxed int,并且不会抛出异常.

Id列绝对是int类型;为什么SELECT @@ IDENTITY会返回小数？

一些其他信息：

>数据库是全新的.
> Customers表是我添加到它的唯一对象.数据库中没有其他(用户)表,视图,触发器或存储过程.
>数据库中有10行,其中Id是1,2,3,4,5,6,7,8,9,10(即列不超出int的限制).

我的表定义是

CREATE TABLE [dbo].[Customers](
    [Id] [int] IDENTITY(1,1) NOT NULL,[Type] [int] NOT NULL,[Name] [nvarchar](255) NOT NULL,[Address] [nvarchar](1000) NOT NULL,[ContactName] [nvarchar](255) NOT NULL,[ContactNumber] [nvarchar](50) NOT NULL,[ContactEmail] [nvarchar](255) NOT NULL,[Supplier] [nvarchar](255) NOT NULL,CONSTRAINT [PK_Customers] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
)WITH (
    PAD_INDEX  = OFF,STATISTICS_NORECOMPUTE  = OFF,IGNORE_DUP_KEY = OFF,ALLOW_ROW_LOCKS  = ON,ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]