Question

I have a Stored Procedure that look like this

BEGIN
insert into `TheSomaProject`.`Projects` 
( `ProjectNr`, `MachineName`, `MachineNameEng`, `Type_Id`, 
  `SerialNr`, `Description`, `Created`, `CompanyId`, `MachineType` ) 
values 
( param_ProjectNr, param_MachineName, param_MachineNameEng, param_TypeId, 
  param_Serial, param_Description, NOW(), param_CompId, param_MachineType); 
SELECT last_insert_id(); 
END

But the return dosent give me the Id, it’s looks like this 0x00000000. The C# code look like this

MySqlDataReader Reader;
MySql.Data.MySqlClient.MySqlCommand cmd = new MySql.Data.MySqlClient.MySqlCommand();
cmd.Connection = conn;
cmd.CommandText = "CALL stp_InsertProject(@param_ProjectNr, @param_MachineName, @param_MachineNameEng, @param_TypeId, @param_Serial, @param_Description, @param_CompId, @param_MachineType);";
cmd.Parameters.AddWithValue("@param_ProjectNr", projectNr);
cmd.Parameters.AddWithValue("@param_MachineName", MachineName);
cmd.Parameters.AddWithValue("@param_MachineNameEng", MachineNameEng);
cmd.Parameters.AddWithValue("@param_TypeId", TypeId);
cmd.Parameters.AddWithValue("@param_Serial", SerialNr);
cmd.Parameters.AddWithValue("@param_Description", Description);
cmd.Parameters.AddWithValue("@param_CompId", CompanyId);
cmd.Parameters.AddWithValue("@param_MachineType", MachineType);
conn.Open();
Reader = cmd.ExecuteReader();
while (Reader.Read())
{
    Id = Convert.ToInt32(Reader["last_insert_id()"]);
}
conn.Close();

But if i try to use the same stp_InsertProject in phpMyAdmin i get the correct id back.

Answer 1

Your stored procedure does not return a result set with a column named ‘last_insert_id()’, thus using an MySqlDataReader will not work (as you expect).

Use ExecuteScalar() to get the result. Note that the value returned is actually a 64-bit integer, so should use a Int64 (or long) type to hold the result:

Int64 lastInsertId = (Int64)cmd.ExecuteReader();

If you need to have a Int32 variable, and thus risk the overflow if too many rows are inserted, make sure you don’t directly cast to Int32 (or int) as this will cause an InvalidCastException since the return type isn’t really Int32 but Int64. In this case use Convert.ToInt32. But I would really suggest that you use a 64 bit integer.