Attempt to call stored function "dbname"."functionname" w/o specifying a return parameter

Question

How can I fix this issue? Am i missing with my code or function code?

Here is my C# code

public int AddDetails(string business, string clerkid, string serverid, string ticket, string tablenumber,
        string sourcecard, string recipientcard, DateTime datesaved, string status)
    {
        CreateConnection();
        int dbId = 0;
        using(cmd = new MySqlCommand())
        {
            cmd.Connection = cn;
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.CommandText = "AddDetails";
            cmd.Parameters.AddWithValue("m_business", business);
            cmd.Parameters.AddWithValue("m_clerkid", clerkid);
            cmd.Parameters.AddWithValue("m_serverid", serverid);
            cmd.Parameters.AddWithValue("m_ticket", ticket);
            cmd.Parameters.AddWithValue("m_tablenumber", tablenumber);
            cmd.Parameters.AddWithValue("m_sourcecard", sourcecard);
            cmd.Parameters.AddWithValue("m_recipientcard", recipientcard);
            cmd.Parameters.AddWithValue("m_datesaved", datesaved);
            cmd.Parameters.AddWithValue("m_status", status);
            cn.Open();
            //dbId = Convert.ToInt32(cmd.LastInsertedId);
            dbId = int.Parse(cmd.ExecuteScalar().ToString());
            //dbId = Convert.ToInt32(cmd.ExecuteNonQuery());
            cn.Close();
        }
        return dbId;
    }

And here is my stored function

 CREATE DEFINER=`root`@`192.168.21.%` FUNCTION `AddDetails`(
m_business VARCHAR(1),
m_clerkid VARCHAR(45),
m_serverid VARCHAR(45),
m_ticket VARCHAR(45),
m_tablenumber VARCHAR(45),
m_sourcecard VARCHAR(45),
m_recipientcard VARCHAR(45),
m_datesaved DATETIME,
m_status VARCHAR(45)
) RETURNS int(11)
    READS SQL DATA
BEGIN
    INSERT INTO `tbl_merchantwarehouse_transaction`
(
`business`,
`clerkid`,
`serverid`,
`ticket`,
`tablenumber`,
`sourcecardnumber`,
`recipientcardnumber`,
`datesaved`,
`status`
)
VALUES(
m_business,
m_clerkid,
m_serverid,
m_ticket,
m_tablenumber,
m_sourcecard,
m_recipientcard,
m_datesaved,
m_status
);

RETURN LAST_INSERT_ID();
END

Any suggestions, advice / improvements to my code will be much appreciated. thank you :D

Answer 1

You should specify the return parameter with your command like:

cmd.Parameters.Add("@ireturnvalue", MySqlDbType.Int32);
cmd.Parameters["@ireturnvalue"].Direction = ParameterDirection.ReturnValue;

Answer 2

You can't use the return value of the ExecuteScalar function - you need to return the paramater value of the returnValue:

public async Task<int> ExecuteIntScalarAsync(string functionName, IEnumerable<MySqlParameter> parameters)
    {
    using (var con = new MySqlConnection({connectionString}))
    {
        await con.OpenAsync();
        MySqlCommand cmd = new MySqlCommand(functionName) { CommandType = System.Data.CommandType.StoredProcedure, Connection = con };

        if (parameters != null)
           foreach (var parameter in parameters)
               cmd.Parameters.Add(parameter);
        var returnValue = new MySqlParameter("returnvalue", MySqlDbType.Int32);
        returnValue.Direction = ParameterDirection.ReturnValue;

        await cmd.ExecuteScalarAsync();
        return (int)returnValue.Value;
    }
}