Question

I want to ask more to show data from SQL Server to WinForm using a datagrid.
I’ve been creating a datagrid and the stored procedure to show data is

ALTER PROC [dbo].[SP_GetData]
AS
  SELECT nama , nim
  FROM tabledata

and I’ve created the function to access the database and the stored procedure in C#

string Sp_Name = "dbo.SP_GetData";

SqlConnection SqlCon = new SqlConnection("Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=DBMahasiswa;Data Source=.");
SqlCon.Open();

SqlCommand SqlCom = new SqlCommand(Sp_Name , SqlCon);
SqlCom.CommandType = CommandType.StoredProcedure;

List<mahasiswaData> listMahasiswa = new List<mahasiswaData>();

using (SqlDataReader sqlDataReader = SqlCom.ExecuteReader())
{
   if (sqlDataReader.HasRows)
   {
      while (sqlDataReader.Read())
      {
         mahasiswaData DataMhs = new mahasiswaData();
         DataMhs.Nama = sqlDataReader["Name"].ToString();
         DataMhs.Umur = Convert.ToInt32(sqlDataReader["Age"]);
         listMahasiswa.Add(DataMhs);
      }
   }
}

SqlCon.Close();
return listMahasiswa;

and finally, in the show button I add this code

dgvmahasiswa.DataSource = new MahasiswaDB().LoadMahasiswa();

Could somebody tell me where the fault is or the alternatives one?

Thank You So Much! 😀

Answer 1

Some things to think about:

1. At the moment, if your code runs into exceptions, you’ll leave a
   SqlConnection hanging around; you’ve used the using pattern for your
   SqlDataReader; you should extend it to all of your disposable
   objects.

2. You are swallowing exceptions; if your query fails, the connection
   cannot be made, or something else happens, you’ll never really know – your function will just return null.

3. Is it possible for name or age to be null? Age to be non-numeric?
   There’s no test for any unexpected values, which you’ll also never
   know about.

4. If you don’t have any records, you’ll return an empty list. Is this
   desired? Or would you prefer to know there were no records?

You might prefer to look at something like this:

public List<mahasiswaData> GetData(){


    List<mahasiswaData> gridData = new List<mahasiswaData>();


    try{

        using(SqlConnection conn = new SqlConnection("Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=DBMahasiswa;Data Source=."))
        {
            using(SqlCommand command = new SqlCommand())
            {
                command.Connection = conn;
                command.CommandType = CommandType.StoredProcedure;
                command.Text = "dbo.SP_GetData";

                using(SqlDataReader reader = command.ExecuteReader())
                {
                    if(reader.HasRows){
                        while(reader.Read())
                        {
                           object rawName = reader.GetValue(reader.GetOrdinal("Name"));
                           object rawAge = reader.GetValue(reader.GetOrdinal("Age"));

                           if(rawName == DBNull.Value || rawAge == DBNull.Value)
                           {
                               //Use logging to indicate name or age is null and continue onto the next record
                               continue;
                           }
                           //Use the object intializer syntax to create a mahasiswaData object inline for simplicity
                           gridData.Add(new mahasiswaData()
                                                   {
                                Nama = Convert.ToString(rawName),
                                                        Umur = Convert.ToInt32(rawAge) 
                                                   });


                        }
                    }
                    else{
                        //Use logging or similar to record that there are no rows. You may also want to raise an exception if this is important.
                    }

                }

            }


        }


    }
    catch(Exception e)
    {
       //Use your favourite logging implementation here to record the error. Many projects use log4Net
       throw; //Throw the error - display and explain to the end user or caller that something has gone wrong!
    }


    return gridData;


}

Note that if you are sure that age or name will never be null then you can simplify the middle section:

while (reader.Read())
{
    //Use the object intializer syntax to create a mahasiswaData object inline for simplicity
    gridData.Add(new mahasiswaData()
    {
        Nama = reader.GetString(reader.GetOrdinal("Name")),
        Umur = reader.GetInt32(reader.GetOrdinal("Age"))
    });

}