SCOPE_IDENTITY not working in asp.net?

Question

I am trying to insert a record and get its newly generated identifier by doing two queries one by one, but I don’t know why it gave me the following error.

Object cannot be cast from DBNull to other types

My code is as follows: (I do not want to use sql stored procedures)

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();
            }
        }
    }

And also, if possible, check if the code is specified correctly, or can we optimize it to improve performance?

thanks

Answer 1

Calling SCOPE_IDENTITY () is not considered to be in the same "scope" as the INSERT command that you are executing.

Essentially, you need to change the line:

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

in

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

and then call

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

.ExecuteNonQuery , "// id".

Answer 2

SCOPE_IDENTITY() (SELECT, RETURN OUT) . , SELECT_IDENTITY() first. SQL 2008 INSERT, .

: , .