How can I convert database query results to an arr

问题:

How would I convert the results returned in a MySQL query to an array in C# .Net/Mono

To my understanding you need to define arrays with the number of items the array will hold but I understand that the DataReader doesn't tell you have many row was returned. so how can I define a array.

So far I have:

string sqlWhere;

        if ((name != None) && (name != ""))
            sqlWhere = "WHERE name LIKE '%"+name+"%'";

        if ((company != None) && (company != ""))
            if (sqlWhere == "")
                sqlWhere = "WHERE company LIKE '%"+company+"%'";
            else
                sqlWhere = sqlWhere + " AND company LIKE '%"+company+"%'";

        if ((dateFrom != None) && (dateFrom != "") && (dateTo != None) && (dateTo != ""))
            if (sqlWhere == "")
                sqlWhere = "WHERE date(timestampIn) BETWEEN '"+dateFrom+"' AND '"+dateTo+"'";
            else
                sqlWhere = sqlWhere + " AND date(timestampIn) BETWEEN '"+dateFrom+"' AND '"+dateTo+"'";

        IDbCommand dbcmd = this.dbcon.CreateCommand();
        dbcmd.CommandText = "SELECT * FROM visitors " + sqlWhere;

                    MySqlDataReader Reader = dbcmd.ExecuteReader();

                    while (Reader.Read())
            {

            }

回答1:

public IList<Group> GetGroup()
        {
            Connection c = new Connection();
            String connectionString = c.ConnectionName;
            OleDbConnection conn = new OleDbConnection(connectionString);
            OleDbCommand mycmd = conn.CreateCommand();
            DataSet dspendingapps = new DataSet();
            dspendingapps.Clear();

            mycmd.CommandText = " select g.groupid,g.groupname from tbl_group g order by g.groupname ";
            conn.Open();

            OleDbDataAdapter appreader = new OleDbDataAdapter(mycmd);
            appreader.Fill(dspendingapps);
            conn.Close();

            IList<Group> g = new List<Group>();

            foreach (DataRow drapp in dspendingapps.Tables[0].Rows)
            {
                Group gg = new Group();
                gg.GroupId = Convert.ToInt16(drapp["groupid"]);
                gg.Name = drapp["groupname"].ToString();
                g.Add(gg);

            }
            return g;
        }

回答2:

Instead of using a DataReader, use a DataAdapter to fill a DataTable. You can see the total number of rows in the resulting DataTable.

var results = new DataTable();

var adapter = new SqlDataAdapter();
adapter.SelectCommand = dbcmd;
dapater.Fill(results);

回答3:

You can use List<T> enter code here instead of array to store your data where T is the type of data you want to store e.g. string, int or your custom data type. For using Arrays, we need to specify the length at compile time but with List<T> we can store data without worrying about the length.

回答4:

Expanding on @Deepansh Gupta's response: You might consider creating a custom object or structure whose internal data fields correspond to the columns returned in your query result set (i.e., each object corresponds to a data row, each data variable in the object corresponds to columnar data). As your code goes through each row of the results, create a new custom object and append it to your List.