从SQL查询设置对象值

Question

I am trying to iterate through an SQL query and set the objects parameters to particular values. The only value that seems to be functioning correctly is the workpack.JobCardIDs, as I can implement a foreach loop to display the results. If I try to set a Label's Text property to a workpack.WorkPackTitle for example, it will display a blank even though the database value is something for every line.

I am fairly new to the OOP so not entirely sure if there is something I am missing that's fundamental.

    public class WorkPack
    {
        public int ID { get; set; }
        public string WorkPackNumber { get; set; }
        public string WorkPackTitle { get; set; }
        public string WorkPackDescription { get; set; }
        public Boolean IFC { get; set; }
        public string SPA { get; set; }
        public string Writer { get; set; }
        public string Organization { get; set; }
        public List<int> JobCardIDs { get; set; }
        public int JobCard { get; set; }
    }

    public static WorkPack PopulateWorkPackObject(WorkPack workpack, int workPackID)
    {
        string ConnectionString = ConfigurationManager.ConnectionStrings["vmdatamanagerConnectionString"].ConnectionString;
        string sqlCall = "I HAVE REMOVED CALL BUT VERIFIED IT FUNCTIONS (SELECT columns FROM workpackdatabase where workpackname = x";

        using (SqlConnection con = new SqlConnection(ConnectionString))
        {
            using (SqlCommand cmd = new SqlCommand(sqlCall, con))
            {
                cmd.Connection.Open();
                using (SqlDataReader reader = cmd.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        if (reader.IsDBNull(reader.GetOrdinal("PARAM1")) == false)
                            workpack.WorkPackNumber = (reader.GetString(reader.GetOrdinal("PARAM1")));

                        if (reader.IsDBNull(reader.GetOrdinal("PARAM2")) == false)
                            workpack.WorkPackTitle = reader.GetString(reader.GetOrdinal("PARAM2"));

                        if (reader.IsDBNull(reader.GetOrdinal("PARAM3")) == false)
                            workpack.WorkPackDescription = reader.GetString(reader.GetOrdinal("PARAM3"));

                        if (reader.IsDBNull(reader.GetOrdinal("PARAM4")) == false)
                            workpack.IFC = reader.GetBoolean(reader.GetOrdinal("PARAM4"));

                        if (reader.IsDBNull(reader.GetOrdinal("PARAM5")) == false)
                            workpack.SPA = reader.GetString(reader.GetOrdinal("PARAM5"));

                        if (reader.IsDBNull(reader.GetOrdinal("PARAM6")) == false)
                            workpack.Writer = reader.GetString(reader.GetOrdinal("PARAM6"));

                        if (reader.IsDBNull(reader.GetOrdinal("PARAM7")) == false)
                            workpack.Organization = reader.GetString(reader.GetOrdinal("PARAM7"));

                        if (reader.IsDBNull(reader.GetOrdinal("PARAM8")) == false)
                            jobCardIDs.Add(reader.GetInt32(reader.GetOrdinal("PARAM8")));

                    }
                    workpack.JobCardIDs = jobCardIDs;
                    return workpack;
                }
            }
        }
    }

Answer 1

Looks like you never create a local instance of your jobCardIDs List. You'll want to do this just inside your ExecuteReader block. See below. GL

public static WorkPack PopulateWorkPackObject(WorkPack workpack, int workPackID)
{
    string ConnectionString = ConfigurationManager.ConnectionStrings["vmdatamanagerConnectionString"].ConnectionString;
    string sqlCall = "I HAVE REMOVED CALL BUT VERIFIED IT FUNCTIONS (SELECT columns FROM workpackdatabase where workpackname = x";

    using (SqlConnection con = new SqlConnection(ConnectionString))
    {
        using (SqlCommand cmd = new SqlCommand(sqlCall, con))
        {
            cmd.Connection.Open();
            using (SqlDataReader reader = cmd.ExecuteReader())
            {
                List<int> jobCardIDs = new List<int>(); //<--***THIS IS THE LINE YOU NEED TO ADD***
                while (reader.Read())
                {
                    if (reader.IsDBNull(reader.GetOrdinal("PARAM1")) == false)
                        workpack.WorkPackNumber = (reader.GetString(reader.GetOrdinal("PARAM1")));

                    if (reader.IsDBNull(reader.GetOrdinal("PARAM2")) == false)
                        workpack.WorkPackTitle = reader.GetString(reader.GetOrdinal("PARAM2"));

                    if (reader.IsDBNull(reader.GetOrdinal("PARAM3")) == false)
                        workpack.WorkPackDescription = reader.GetString(reader.GetOrdinal("PARAM3"));

                    if (reader.IsDBNull(reader.GetOrdinal("PARAM4")) == false)
                        workpack.IFC = reader.GetBoolean(reader.GetOrdinal("PARAM4"));

                    if (reader.IsDBNull(reader.GetOrdinal("PARAM5")) == false)
                        workpack.SPA = reader.GetString(reader.GetOrdinal("PARAM5"));

                    if (reader.IsDBNull(reader.GetOrdinal("PARAM6")) == false)
                        workpack.Writer = reader.GetString(reader.GetOrdinal("PARAM6"));

                    if (reader.IsDBNull(reader.GetOrdinal("PARAM7")) == false)
                        workpack.Organization = reader.GetString(reader.GetOrdinal("PARAM7"));

                    if (reader.IsDBNull(reader.GetOrdinal("PARAM8")) == false)
                        jobCardIDs.Add(reader.GetInt32(reader.GetOrdinal("PARAM8")));

                }
                workpack.JobCardIDs = jobCardIDs;
                return workpack;
            }
        }
    }
}

Answer 2

The previous answers given by the community did not fix the issue, although I did put that extra snippet it.

The issue was when the objects were being created and passed between post backs. The object would be relevant on selection of the job card tab but once the page loaded there was no code to rebuild that instance.

Adding

      Object foo = new Object();

in the page_Load() and rebuilding fixed the issue. If anyone has any suggestions on how to keep an instance alive I am all for hearing it. I think ViewState() and also Session[] were applicable methods for doing so.