use*_*285 3 c# sql-server ado.net

我遇到错误
将数据类型nvarchar转换为数字时出错。
表值参数“ @dt”的数据不符合该参数的表类型。
我创建了一个SQL Server表类型:
CREATE TYPE NACVCC AS TABLE
(
CurrentNACV decimal(5,3),
Year1NACV decimal(5,3),
Year2NACV decimal(5,3),
Year3NACV decimal(5,3),
Year4NACV decimal(5,3),
Year5NACV decimal(5,3),
NACVText nvarchar(255)
);
GO
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存储过程为:
CREATE PROCEDURE dbo.InsertNACVCC
@dt AS dbo.NACVCC READONLY
AS
BEGIN
SET NOCOUNT ON;
TRUNCATE TABLE GPSNACVCC
INSERT dbo.GPSNACVCC(NACVText, CurrentNACV, Year1, Year2, Year3, Year4, Year5)
SELECT
NACVText, CurrentNACV,
Year1NACV, Year2NACV, Year3NACV, Year4NACV ,Year5NACV
FROM @dt;
END
GO
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从C#中我这样调用:
public static void InsertUSNACVCC(DataTable tvp)
{
using (SqlConnection con = new SqlConnection(GetConnectionString()))
{
con.Open();
SqlCommand cmd = new SqlCommand("dbo.InsertNACVCC", con);
cmd.CommandType = CommandType.StoredProcedure;
SqlParameter tvparam = cmd.Parameters.AddWithValue("@dt", tvp);
tvparam.SqlDbType = SqlDbType.Structured;
cmd.ExecuteNonQuery();
}
}
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Cmd.ExecuteNonQuery()返回提到的错误。我已经匹配了类型nvarchar(255)和表中的数据类型。
请帮忙