mysqlstored-proceduresentity-framework-coreoutput-parameterinput-parameters

How to call stored procedure in Entity Framework Core with input and output parameters using mysql


I am using ASP.net Core 2.2 with Entity Framework core 2.2.6 and Pomelo.EntityFrameworkCore.MySql 2.2.0 for connectivity with MySQL, I have a stored procedure which takes 3 input parameters and 1 output parameter. I am able to call it in MySQL workbench like

CALL GetTechniciansByTrade('Automobile', 1, 10, @total);
select @total;

Now I want to call this using entity framework core, the code I am currently using is

var outputParameter = new MySqlParameter("@PageCount", MySqlDbType.Int32);
outputParameter.Direction = System.Data.ParameterDirection.Output;

var results = await _context.GetTechnicians.FromSql("Call GetTechniciansByTrade(@MyTrade, @PageIndex, @PageSize, @PageCount OUT)",
new MySqlParameter("@MyTrade", Trade),
new MySqlParameter("@PageIndex", PageIndex),
new MySqlParameter("@PageSize", PageSize),
outputParameter).ToListAsync();

int PageCount = (int)outputParameter.Value;

Exception I am getting currently is

Only ParameterDirection.Input is supported when CommandType is Text (parameter name: @PageCount)


Solution

  • I found the solution using @matt-g suggestion based on this Question. I had to use ADO.net for this as

    var technicians = new List<TechnicianModel>();
    using (MySqlConnection lconn = new MySqlConnection(_context.Database.GetDbConnection().ConnectionString))
    {
        lconn.Open();
        using (MySqlCommand cmd = new MySqlCommand())
        {
            cmd.Connection = lconn;
            cmd.CommandText = "GetTechniciansByTrade"; // The name of the Stored Proc
            cmd.CommandType = CommandType.StoredProcedure; // It is a Stored Proc
    
            cmd.Parameters.AddWithValue("@Trade", Trade);
            cmd.Parameters.AddWithValue("@PageIndex", PageIndex);
            cmd.Parameters.AddWithValue("@PageSize", PageSize);
    
            cmd.Parameters.AddWithValue("@PageCount", MySqlDbType.Int32);
            cmd.Parameters["@PageCount"].Direction = ParameterDirection.Output; // from System.Data
    
            using (var reader = cmd.ExecuteReader())
            {
                while (reader.Read())
                {
                    technicians.Add(new TechnicianModel()
                    {
                        City = reader["City"].ToString(),
                        ExperienceYears = reader["ExperienceYears"] != null ? Convert.ToInt32(reader["ExperienceYears"]) : 0,
                        Id = Guid.Parse(reader["Id"].ToString()),
                        Name = reader["Name"].ToString(),
                        Qualification = reader["Qualification"].ToString(),
                        Town = reader["Town"].ToString()
                    });
                }
            }
    
            Object obj = cmd.Parameters["@PageCount"].Value;
            var lParam = (Int32)obj;    // more useful datatype
        }
    }