将查询结果存储在字典中

Question

I have problem to develop Windows mobile app using C#, I trying to work with 3 query. I want to collect all result query into Dictionary.

can i collect it without looping?

like this my code:

string query= "select distinct nameProduct, price from product";
SqlCeCommand cmd = new SqlCeCommand(sql, dbConn);
Dictionary production = new Dictionary<string, int>();

How can i set this production from my query, becausei have 3 query like this in one process and the data is more than 10.000.

@John Saunders: when i try this, i get error"{"No data exists for the row/column."}" but actually when i try the query in sql server still running well. the error in the line: production[(string)reader["nameProduct"]] = (int)reader["price"];

@Johnny: unfortunatelly this project build in VS2005 and not support union and join statement.

Answer 1

Dictionary production = new Dictionary<string, int>();
string query= "select distinct nameProduct, price from product";
using (SqlCeCommand cmd = new SqlCeCommand(sql, dbConn))
{
    using (var reader = cmd.ExecuteReader())
    {
        while (reader.Read())
        {
            production[(string)reader["nameProduct"]] = (int)reader["price"];
        }
    }
}

Without a loop. Note I haven't tried it:

production =
    reader.Cast<IDataRecord>()
          .ToDictionary(
              record => (string)record["nameProduct"], 
              record => (int)record["price"]);

Answer 2

This is the simple way to fetch data from database and store data in dictionary

Dictionary<int, string>emp = new Dictionary<int, string>();
OleDbCommand cmd = new OleDbCommand("select empId,Name from Employee where ORDER BY empId DESC", con);
OleDbDataReader dr = cmd.ExecuteReader();

if (dr.HasRows)
{
    while (dr.Read())
    {
         emp.Add(Convert.ToInt32(dr["empId"]), dr["Name"].ToString());                
    }                    
}

foreach (KeyValuePair<int, string> em in emp)
{
    Console.WriteLine(em.Key.ToString() + " = " + em.Value);
}

Answer 3

You may convert DataTable (use DataAdapter.Fill method to populate the DataTable) result into Dictionay.

string query= "select distinct nameProduct, price from product";
SqlCeConnection conn = new SqlCeConnection("Data Source = your file.sdf");

SqlCeCommand selectCmd = conn.CreateCommand();
selectCmd.CommandText = query;

SqlCeDataAdapter adp = new SqlCeDataAdapter(selectCmd);
DataTable dt=new DataTable();
adp.Fill(dt);

Dictionary<string, int> result = (from row in dt.AsEnumerable()
                          select new KeyValuePair<string, int>
                          (row.Field<string>("nameProduct"), row.Field<int>("price")))
                          .ToDictionary(p=>p.Key,p=>p.Value);

 foreach (var t in result)
  {
    Console.WriteLine(t.Key + " " + t.Value);
  }

Answer 4

A few points.

1.I think you can use "union all" in your query. 2.If you have more than 10000 rows of record,especially on a mobile device, I will suggest you to only load those data you need, and you can display with in one screen, instead of read all.