问题描述

我收到异常:特定转换无效"，这是代码

I am getting exception: "Specific cast is not valid", here is the code

con.Open();
string insertQuery = @"Insert into Tender (Name, Name1, Name2) values ('Val1','Val2','Val3');Select Scope_Identity();";

SqlCommand cmd = new SqlCommand(insertQuery, con);
cmd.ExecuteNonQuery();
tenderId = (int)cmd.ExecuteScalar();

推荐答案

为了完整起见，您的代码示例存在三个问题.

In the interests of completeness, there are three issues with your code sample.

1) 您通过调用 ExecuteNonQuery 和 ExecuteScalar 执行了两次查询.因此，每次运行此函数时，您都将在表中插入两条记录.您的 SQL 虽然是两条不同的语句，但将一起运行，因此您只需要调用 ExecuteScalar.

1) You are executing your query twice by calling ExecuteNonQuery and ExecuteScalar. As a result, you will be inserting two records into your table each time this function runs. Your SQL, while being two distinct statements, will run together and therefore you only need the call to ExecuteScalar.

2) Scope_Identity() 返回一个小数.您可以对查询结果使用 Convert.ToInt32，也可以将返回值转换为十进制然后转换为 int.

2) Scope_Identity() returns a decimal. You can either use Convert.ToInt32 on the result of your query, or you can cast the return value to decimal and then to int.

3) 确保将您的连接和命令对象包装在 using 语句中，以便正确处理它们.

3) Be sure to wrap your connection and command objects in using statements so they are properly disposed.

using (SqlConnection connection = new SqlConnection(connectionString))
{
    using (SqlCommand command = new SqlCommand(sql, connection))
    {
        connection.Open();
        int tenderId = (int)(decimal)command.ExecuteScalar();
    }
}

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