SCOPE_IDENTITY无法在asp.net中运行？

Question

我试图通过逐个执行两个查询来插入记录并获取其新生成的id,但不知道为什么它给我以下错误.

Object cannot be cast from DBNull to other types

我的代码如下:(我不想使用sql存储过程)

SqlParameter sqlParam;
    int lastInsertedVideoId = 0;

    using (SqlConnection Conn = new SqlConnection(ObjUtils._ConnString))
    {
        Conn.Open();
        using (SqlCommand sqlCmd = Conn.CreateCommand())
        {
            string sqlInsertValues = "@Name,@Slug";
            string sqlColumnNames = "[Name],[Slug]";
            string sqlQuery = "INSERT INTO videos(" + sqlColumnNames + ") VALUES(" + sqlInsertValues + ");";
            sqlCmd.CommandText = sqlQuery;
            sqlCmd.CommandType = CommandType.Text;

            sqlParam = sqlCmd.Parameters.Add("@Name", SqlDbType.VarChar);
            sqlParam.Value = txtName.Text.Trim();

            sqlParam = sqlCmd.Parameters.Add("@Slug", SqlDbType.VarChar);
            sqlParam.Value = txtSlug.Text.Trim();


            sqlCmd.ExecuteNonQuery();

            //getting last inserted video id
            sqlCmd.CommandText = "SELECT SCOPE_IDENTITY() AS [lastInsertedVideoId]";
            using (SqlDataReader sqlDr = sqlCmd.ExecuteReader())
            {
                sqlDr.Read();
                lastInsertedVideoId = Convert.ToInt32(sqlDr["lastInsertedVideoId"]);
            }
        }
    }

    //tags insertion into tag table
    if (txtTags.Text.Trim().Length > 0 && lastInsertedVideoId > 0)
    {
        string sqlBulkTagInsert = "";
        string[] tags = txtTags.Text.Split(new string[] { "," }, StringSplitOptions.RemoveEmptyEntries);
        foreach (string tag in tags)
        {
            sqlBulkTagInsert += "INSERT INTO tags(VideoId, Tag) VALUES(" + lastInsertedVideoId + ", " + tag.Trim().ToLowerInvariant()+ "); ";
        }

        using (SqlConnection Conn = new SqlConnection(ObjUtils._ConnString))
        {
            Conn.Open();
            using (SqlCommand sqlCmd = Conn.CreateCommand())
            {
                string sqlQuery = sqlBulkTagInsert;
                sqlCmd.CommandText = sqlQuery;
                sqlCmd.CommandType = CommandType.Text;

                sqlCmd.ExecuteNonQuery();
            }
        }
    }

如果可能的话,请检查以上代码编码是否正确,或者我们可以进一步优化它以提高性能？

谢谢

Answer 1

对SCOPE_IDENTITY()的调用不会被视为与您正在执行的INSERT命令位于相同的"范围"中.

基本上,您需要做的是更改线路:

string sqlQuery = "INSERT INTO videos(" + sqlColumnNames + ") VALUES(" + sqlInsertValues + ");";

至:

string sqlQuery = "INSERT INTO videos(" + sqlColumnNames + ") VALUES(" + sqlInsertValues + "); SELECT SCOPE_IDENTITY() AS [lastInsertedVideoId]";

然后打电话

int lastVideoInsertedId = Convert.ToInt32(sqlCmd.ExecuteScalar());

而不是.ExecuteNonQuery和"//获取最后插入的视频ID"注释后面的代码块.