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How to create array of type with having list of object similar type in C#

We have third party class which only accepts arrays of object.
Third Party class :
public class Test
{
public class Input
{
public int testVar { get; set; }
public int testVar2 { get; set; }
}
//some methods
public static List<someType> Convert(Input[] data)
{
//execute some steps
}
}
in DB, we have the data column which we are interested and it has thousand of records.
Id data
1 new Test.Input{ testVar=12,testVar=19}
2 new Test.Input{ testVar=16,testVar=12}
3 new Test.Input{ testVar=26,testVar=11}
-
i am trying to create a class and invoke Convert method of Test class by providing array of Input type object .
public class ImplementTest
{
public void CallConvert()
{
// get the data from DB in list
List<object> Input = new List<object>();
using (SqlConnection con = new SqlConnection(conString))
{
using (SqlCommand cmd = new SqlCommand())
{
cmd.CommandType = System.Data.CommandType.StoredProcedure;
cmd.CommandText = "dbo.ReadAll_Input";
con.Open();
using (SqlDataReader dr = cmd.ExecuteReader())
{
while (dr.Read())
{
Input.Add(dr["data"]);
}
}
}
}
//convert list object to input type object
var inputs = new Test.Input[]
{
//how to pass Input list efficiently
};
var output = Test.Convert(inputs).ToArray();
}
}
can anyone help me on passing Input list object to Create array of object efficiently please?
Thanks!

You can use a Mapper method:
public Input MapRow(IDataRecord row)
{
return new Input
{
Name = row["Name"].ToString(),
Number = int.Parse(row["Number"].ToString())
};
}
And use it like this:
public void CallConvert()
{
// get the data from DB in list
List<Input> inputs = new List<Input>();
using (SqlConnection con = new SqlConnection(conString))
{
using (SqlCommand cmd = new SqlCommand())
{
cmd.CommandType = System.Data.CommandType.StoredProcedure;
cmd.CommandText = "dbo.ReadAll_Input";
con.Open();
using (SqlDataReader dr = cmd.ExecuteReader())
{
while (dr.Read())
{
inputs.Add(MapRow(dr));
}
}
}
}
var output=Test.Convert(inputs.ToArray());
}
And to make it work, your stored procedure should return a table of inputs with, in this case, two columns (Name, Number)

ADO.NET DAL and BLL

I have two classes SqlHelper and DishesTypes there are used in a DAL project
public class SqlHelper
{
public static SqlDataReader ExecuteReader(string procedure,
params SqlParameter[] commandParameters)
{
using (var connection = new SqlConnection(
ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString))
using (var command = new SqlCommand(procedure, _connection))
{
command.CommandType = CommandType.StoredProcedure;
command.Parameters.AddRange(commandParameters);
return command.ExecuteReader();
}
}
public class DishesTypes
{
public static SqlDataReader DishesTypesSelectAll()
{
return SqlHelper.ExecuteReader("DishesTypesSelectAllRows"); //name of procedure
}
}
And I have class DishedTypes that used in a BLL project like this
public class DishesTypes
{
public int DishTypeId { get; set; }
public string DishType { get; set; }
public static List<DishesTypes> DishesTypesSelectAll()
{
IDataReader dr = DataAccessLayer.DishesTypes.DishesTypesSelectAll();
List<DishesTypes> dishesTypesList = new List<DishesTypes>();
while (dr.Read())
{
DishesTypes myDishesTypes = new DishesTypes
{
DishTypeId = (int)dr["DishTypeId"],
DishType = (string)dr["DishType"]
};
dishesTypesList.Add(myDishesTypes);
}
return dishesTypesList;
}
}
Problems starts here while (dr.Read()),The reason, the connection to this point has already closed and it is necessary to reconnect how best to change the implementation of classes adhering layers DAL and BLL, to work?

If you want to roll your own, something like this is better:
public class DataQuery
{
private readonly string _connectionString;
public DataQuery(string connectionString)
{
_connectionString = connectionString;
}
public IEnumerable<T> GetList<T>(string procedure,
Func<IDataRecord, T> entityCreator,
params SqlParameter[] commandParameters
)
{
var result = new List<T>();
using (var connection = CreateConnection())
using (var command = CreateCommand(procedure, connection, commandParameters))
using (var reader = command.ExecuteReader())
{
result.Add(entityCreator(reader));
}
return result;
}
private SqlConnection CreateConnection()
{
var connection = new SqlConnection(_connectionString);
connection.Open();
return connection;
}
private static DbCommand CreateCommand(string procedure,
SqlConnection connection, SqlParameter[] commandParameters)
{
var command = new SqlCommand(procedure, connection)
{
CommandType = CommandType.StoredProcedure
};
command.Parameters.AddRange(commandParameters);
return command;
}
}
Which you would call like this:
var connectionString = ConfigurationManager.ConnectionStrings["DefaultConnection"]
.ConnectionString;
var query = new DataQuery(connectionString);
Func<IDataRecord, DishesTypes> creator = dr =>
new DishesTypes
{
DishTypeId = (int)dr["DishTypeId"],
DishType = (string)dr["DishType"]
};
var results = query.GetList("DishesTypesSelectAllRows", creator);
Otherwise, which I recommend, have a look at Dapper.
Dapper would allow you to simply do:
var results = connection.Query<DishesTypes>("DishesTypesSelectAllRows",
commandType: CommandType.StoredProcedure);

First of all, your using statement is closing your connection, so you cannot expect to return a useable IDataReader. Second, your connection is never opened, so you would not get a result, anyway. Having said that, if your dataset will always be small enough to fit in memory, you could use something like what I have done below. This should have minimal impact on your code.
public class SqlHelper
{
public static IDataReader ExecuteReader(string procedure, params SqlParameter[] commandParameters)
{
using (var connection = new SqlConnection(ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString))
{
connection.Open();
using (var command = new SqlCommand(procedure, connection))
{
command.CommandType = CommandType.StoredProcedure;
command.Parameters.AddRange(commandParameters);
DataTable dt = new DataTable();
using (SqlDataAdapter da = new SqlDataAdapter(command))
da.Fill(dt);
return dt.CreateDataReader();
}
}
}
}
public class DishesTypes
{
public static IDataReader DishesTypesSelectAll()
{
return SqlHelper.ExecuteReader("DishesTypesSelectAllRows");//name of procedure
}
}

Close OracleConnection after ExecuteReader

This is my current pattern
private void ReadData(string connString, string cmdString)
{
using (OracleConnection conn = new OracleConnection(connString))
{
conn.Open();
OracleCommand cmd = new OracleCommand(cmdString, conn);
OracleDataReader reader = cmd.ExecuteReader();
//some long operation using reader
}
}
In the above case, the connection remains open while the long operation is going on. Is there a way I could close the connection but still preserve the reader. Is that going to be advantageous?

If by long operations you mean to say that you need to do extra operations on the database (like update/insert/delete), then you cannot close the connection.
If you want to read the data and do some calculation based on it, then you should modify you pattern to: 1. read all the data, 2. close the connection, 3. do long operation on the data.
using System;
using System.Collections.Generic;
using Oracle.DataAccess.Client;
namespace Utils
{
class Test
{
private class Class
{
public string FirstProperty { get; set; }
public string SecondProperty { get; set; }
}
private void ReadData(string connString, string cmdString)
{
List<Class> data = new List<Class>();
using (OracleConnection conn = new OracleConnection() { ConnectionString = connString })
using (OracleCommand objCmd = new OracleCommand()
{
Connection = conn,
CommandText = cmdString
})
{
try
{
conn.Open();
}
catch (OracleException)
{
OracleConnection.ClearPool(conn);
conn.Open();
}
using (OracleDataReader dataReader = objCmd.ExecuteReader())
{
while (dataReader.Read())
data.Add(new Class()
{
FirstProperty = dataReader.GetString(0),
SecondProperty = dataReader.GetString(1)
});
}
conn.Close();
}
//some long operation using data
}
}
}

Importing array values in constructor

In my main form I have the following code
[ImportingConstructor]
public MainForm([ImportMany] IEnumerable<AudioPlugin> content)
{
InitializeComponent();
listBox.DisplayMember = "Name";
foreach (var listing in content)
{
listBox.Items.Add(listing);
}
}
In my AudioPlugin class I have the following code
[Export(typeof(INAudioPlugin))]
public class RecordingPanelPlugin : AudioPlugin
{
private string _customer { get; set; }
public void ConnectionString()
{
using (var conn = new SqlCeConnection("Data Source=MyDatabase.sdf;Password=pass;Persist Security Info=True"))
{
conn.Open();
var comm = new SqlCeCommand("SELECT * FROM main", conn);
SqlCeDataReader reader = comm.ExecuteReader();
while (reader.Read())
{
_customer = (string)(reader["CustomerName"]);
Console.WriteLine(_customer);
}
}
}
public string Name
{
get
{
ConnectionString();
return _customer;
}
}
public Control CreatePanel()
{
return new RecordingPanel();
}
}
With the code as it is, I'm only getting the last value returned from the SQL query. What am I missing?

You're assigning the value of the last read element to the variable _customer, you should use a datastructure (like a List) to keep all the elements you're getting and then pass that to the constructor.
Your code should be fixed this way:
private List<string> _customers = new List<string>();
public void ConnectionString()
{
using (var conn = new SqlCeConnection("Data Source=MyDatabase.sdf;Password=pass;Persist Security Info=True"))
{
conn.Open();
var comm = new SqlCeCommand("SELECT * FROM main", conn);
SqlCeDataReader reader = comm.ExecuteReader();
string customer;
while (reader.Read())
{
customer = (string)(reader["CustomerName"]);
Console.WriteLine(customer);
_customers.Add(customer);
}
}
}

I guess I was over-thinking this problem. I removed the Import/Export from both classes and instead decided to call the query directly in my main form so I could populate the listbox as needed. Then I'm assigning a variable to the listbox.SelectedItem and am passing that over to the AudioPlugin class. Everything is working as expected now, thanks for the suggestions to try and resolve the issue though.

Any way to avoid nesting usings when opening a SqlDataReader?

Not a big deal but for neatness sake is there any way to "create and open" a SqlConnection?
I naively wrote this code:
using (var strConnection = new SqlConnection(sourceConnection))
using (var strCommand = new SqlCommand(query, strConnection))
using (var reader = strCommand.ExecuteReader())
{
...
}
Which of course fails on line 3 because the connection isn't open.
Is there a neat way to avoid that nesting that opening the connection introduces?
using (var strConnection = new SqlConnection(sourceConnection))
{
strConnection.Open();
using (var strCommand = new SqlCommand(query, strConnection))
using (var reader = strCommand.ExecuteReader())
{
...
}
}

Good question, my idea is an Extension-Method for SqlConnection.
Check this:
public static class SqlExtensions {
public static SqlConnection OpenAndReturn(this SqlConnection con) {
try {
con.Open();
return con;
} catch {
if(con != null)
con.Dispose();
throw;
}
}
}
Usage:
using(var strConnection = new SqlConnection("CONNECTION").OpenAndReturn())
using(var strCommand = new SqlCommand("QUERY", strConnection))
using(var reader = strCommand.ExecuteReader()) {
//...
}

What about something like that:
class SqlHelper : IDisposable
{
public SqlHelper(string connectionString, string query) { ... }
public SqlConnection Connection { get; set; }
public SqlCommand Command { get; set; }
// SQL querying logic here
public void Execute() { ... }
/** IDisposable implementation **/
}
and in your code
using (SqlHelper sql = new SqlHelper(sourceConnection, query))
{
var reader = sql.Execute();
...
}