Geek asks and answers

Use SqlDataReader in F #

In C #, I use sql scripts to add data to a list, where T will be a class with fields / properties mapped to sql script.

How can I do this in F #? This part uses the stored procedure in a standard way.

using (conn)
{
    conn.Open();
    using (SqlCommand cmd = new SqlCommand("dbo.query_here", conn))
    {
    cmd.CommandText = "dbo.query_here";
    cmd.CommandType = System.Data.CommandType.StoredProcedure;
    cmd.CommandTimeout = 600;
    cmd.Parameters.Add(new SqlParameter("@x1", Convert.ToString(x)));
    cmd.Parameters.Add(new SqlParameter("@y1", y));
    cmd.Parameters.Add(new SqlParameter("@z1", z));
    SqlDataReader reader = cmd.ExecuteReader();
    while (reader.Read())
    {
        MyListOfClasses.Add(new MyDataClass(reader.GetInt32(reader.GetOrdinal("x"))           
                                            reader.GetDouble(reader.GetOrdinal("y")),
                                            reader.GetDouble(reader.GetOrdinal("a")),
                                            reader.GetDouble(reader.GetOrdinal("b"))));
    }
    reader.Close();
}
conn.Close();

I understand that F # is not so straightforward, perhaps like this, but I need to get this data into F # lists in a similar way. Also would prefer sentences that were not functional in nature and followed a similar pattern with C # code.

In the previous thread, someone suggested using records, but still it did not concern SqlDataReader. It would be preferable to have a list of classes so that I can use getters and setters for each element.

" #". , , #, F # SQL Server.

+5
4

results F #, . use .

use conn = (* Initialize sql connection here *)
conn.Open()
use cmd = new SqlCommand("dbo.query_here", conn)
cmd.CommandText <- "dbo.query_here"
cmd.CommandType <- System.Data.CommandType.StoredProcedure
cmd.CommandTimeout <- 600
cmd.Parameters.Add(new SqlParameter("@x1", Convert.ToString(x)))
cmd.Parameters.Add(new SqlParameter("@y1", y))
cmd.Parameters.Add(new SqlParameter("@z1", z))
use reader = cmd.ExecuteReader()
let results =
 [ while reader.Read() do
    yield new MyDataClass(reader.GetInt32(reader.GetOrdinal("x")),           
                          reader.GetDouble(reader.GetOrdinal("y")),
                          reader.GetDouble(reader.GetOrdinal("a")),
                          reader.GetDouble(reader.GetOrdinal("b"))) ]
+8

ADO.NET F # ?. MSDN, , - :

let myListOfClasses = 
  [ let db = new DynamicDatabase(connectionString)
    let rows = db.Query?query_here(string x, y, z)
    for r in rows do 
      yield MyDataClass(row?x, row?y, row?a, row?b) ]

(db.Query?query_here) ?. , , ( SQL). row?x - MyDataClass, , , .

MSDN, :

+6

Link: http://www.codeproject.com/Articles/95656/Using-a-DataRader-like-a-List-in-F

let rdr = cmd.ExecuteReader()

rdr
|> SomeRecord.asSeq                     // project datareader into seq<SomeRecord>
|> Seq.sumBy (fun r-> r.val1 * r.val2)  // now you can use all the Seq operators 
                                        // that everybody knows.
+3
source

Unconfirmed translation to F #

use conn = ???
conn.Open()
using new SqlCommand("dbo.query_here", conn)(fun cmd ->

    cmd.CommandText <- "dbo.query_here"
    cmd.CommandType <- System.Data.CommandType.StoredProcedure
    cmd.CommandTimeout <- 600
    cmd.Parameters.Add(new SqlParameter("@x1", Convert.ToString(x)))
    cmd.Parameters.Add(new SqlParameter("@y1", y))
    cmd.Parameters.Add(new SqlParameter("@z1", z))
    let reader = cmd.ExecuteReader()
    while (reader.Read()) do
        MyListOfClasses.Add(new MyDataClass(reader.GetInt32(reader.GetOrdinal("x"))           
                                            reader.GetDouble(reader.GetOrdinal("y")),
                                            reader.GetDouble(reader.GetOrdinal("a")),
                                            reader.GetDouble(reader.GetOrdinal("b"))))

    reader.Close()
)
conn.Close()
MyListOfClasses.ToArray() |> List.ofArray
+3
source

More articles:


All Articles