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Reading sql one row at a time c#

public void addintovisitor()
{
string companyname = (txtvisitor.Text.ToUpper());
DataSet result = new DataSet();
visitorcompany vc = new visitorcompany();
string Location1 = Convert.ToString(Session["location"]);
vc.checksamecompanyname(ref result, Location1);
for (int i = 0; i < result.Tables["details"].Rows.Count; i++)
{
if (companyname == result.Tables["details"].Rows[i]["Companyname"].ToString())
{
}
else
{
string strConn = Convert.ToString(ConfigurationManager.ConnectionStrings["connectionstring"]);
SqlConnection conn = new SqlConnection(strConn);
SqlCommand cmd = new SqlCommand(
"INSERT INTO tblVisitorcompany ([CompanyName], " +
"[Location1]) " +
"VALUES(#CompanyName, #Location1)", conn);
cmd.Parameters.AddWithValue("#Companyname", companyname);
cmd.Parameters.AddWithValue("#Location1", Location1);
conn.Open();
cmd.ExecuteNonQuery();
conn.Close();
}
}
}
My visitorcompany class:
public int checksamecompanyname(ref DataSet result, string Location1)
{
string strConn = Convert.ToString(
ConfigurationManager.ConnectionStrings
["connectionstring"]);
SqlConnection conn = new SqlConnection(strConn);
SqlCommand cmd = new SqlCommand
("select Companyname from tblVisitorcompany where Location1 ='" + Location1 + "'", conn);
SqlDataAdapter da = new SqlDataAdapter(cmd);
conn.Open();
da.Fill(result, "details");
conn.Close();
//Return 0 when no error occurs.
return 0;
}
I am trying to search one row at a time to check whether the sql table got the same companyname. if there is already exisiting companyname, the program will do nothing. If this is a new companyname, the program will add companyname into the sql table. However, when adding new companyname, the program will add more than once. Can someone please help me to re-edit my program such that it only add one new companyname. Many thanks.

using( var connection = new SqlConnection( "my connection string" ) ) {
using( var command = connection.CreateCommand() ) {
command.CommandText = "SELECT Column1, Column2, Column3 FROM myTable";
connection.Open();
using( var reader = command.ExecuteReader() ) {
var indexOfColumn1 = reader.GetOrdinal( "Column1" );
var indexOfColumn2 = reader.GetOrdinal( "Column2" );
var indexOfColumn3 = reader.GetOrdinal( "Column3" );
while( reader.Read() ) {
var value1 = reader.GetValue( indexOfColumn1 );
var value2 = reader.GetValue( indexOfColumn2 );
var value3 = reader.GetValue( indexOfColumn3 );
// now, do something what you want
}
}
connection.Close();
}

dont use companyname as an argument of your insert command, since it is stays the same in for loop. Use result.Tables["details"].Rows[i]["Companyname"].ToString() instead:
...
cmd.Parameters.AddWithValue("#Companyname", result.Tables["details"].Rows[i]["Companyname"].ToString());
...

Check if the value exists, then add it if not.
A simple change in your code:
bool valueFound = false;
// check if the value exists
for (int i = 0; i < result.Tables["details"].Rows.Count; i++)
{
if (companyname == result.Tables["details"].Rows[i]["Companyname"].ToString())
{
// it exists so we exit the loop
valueFound = true;
break;
}
}
// we have looped all the way without finding the value, so we can insert
if(!valueFound)
{
string strConn = Convert.ToString(ConfigurationManager.ConnectionStrings["connectionstring"]);
SqlConnection conn = new SqlConnection(strConn);
SqlCommand cmd = new SqlCommand(
"INSERT INTO tblVisitorcompany ([CompanyName], " +
"[Location1]) " +
"VALUES(#CompanyName, #Location1)", conn);
cmd.Parameters.AddWithValue("#Companyname", companyname);
cmd.Parameters.AddWithValue("#Location1", Location1);
conn.Open();
cmd.ExecuteNonQuery();
conn.Close();
}
Off course you could check if the value exists in a more efficient way, but this should at least solve your specific problem.

There is already an open datareader error when filling Gridviews

I have looked at several posts already on trying to fix this issue and none of them are working.
I'm already using multiple active results.
I'm making sure to close the reader connections.
I'm using a different connection.
I'm using unique names for the reader, datatable, the reader, the command...
I am stuck.
The error is: There is already an open DataReader associated with this Command which must be closed first.
I have marked the error line with "*****error here *****".
Code:
protected void gridviewsched_RowDataBound(object sender, GridViewRowEventArgs e)
{
string nametime;
string name;
string time;
string initid;
string timeinitid = null;
GridView gridviewschedsub = (GridView)e.Row.FindControl("gridviewschedsub");
GridView gridviewschedcplt = (GridView)e.Row.FindControl("gridviewschedcplt");
using (SqlConnection con = new SqlConnection("Data Source=localhost\\SQLEXPRESS;AttachDbFilename=C:\\Users\\Public\\public website\\slDataBase.mdf;Integrated Security=True;Trusted_Connection=True; MultipleActiveResultSets=True;"))
{
con.Open();
DataTable dz = new DataTable();
dz.Columns.Add("age");
dz.Columns.Add("sex");
dz.Columns.Add("address");
if (e.Row.RowType == DataControlRowType.DataRow)
{
string id = gridviewsched.DataKeys[e.Row.RowIndex].Value.ToString();
using (var cmd = new SqlCommand("SELECT age,sex,address FROM precordTable WHERE Id='" + id + "'", con))
{
using (SqlDataReader reader = cmd.ExecuteReader())
{
//List<string> namedatelist = new List<string>();
while (reader.Read())
{
DataRow dr = dz.NewRow();
dr["age"] = reader[0].ToString();
dr["sex"] = reader[1].ToString();
dr["address"] = reader[2].ToString();
dz.Rows.Add(dr);
}
reader.Close();
}
gridviewschedsub.DataSource = dz;
gridviewschedsub.DataBind();
con.Close();
}
using (var cmd3 = new SqlCommand("SELECT name, initid FROM precordTable WHERE Id='" + id + "'", con))
{
con.Open();
using (SqlDataReader reader = cmd3.ExecuteReader())
{
List<string> namedatelist = new List<string>();
while (reader.Read())
{
name = reader["name"].ToString();
initid = reader["initid"].ToString();
time = DateTime.Now.ToString("MM-dd-yyyy");
time = Regex.Replace(time, "[^0-9a-zA-Z]+", "");
namedatelist.Add(name + time);
timeinitid = time + "$" + initid;
}
Session["timeinitid"] = timeinitid;
nametime = Regex.Replace(namedatelist[0].ToString(), "[^0-9a-zA-Z]+", "");
reader.Close();
}
}
var cmd2 = new SqlCommand("select case when exists((select * from [C:\\USERS\\PUBLIC\\PUBLIC WEBSITE\\SLDATABASE.MDF].INFORMATION_SCHEMA.tables where table_name = 'D" + timeinitid + "ou')) then 1 else 0 end", con);
if ((int)cmd2.ExecuteScalar() == 1)
{
string fQuery = "select item, scheduled from D" + timeinitid + "ou where 0 = 1";
string pQuery = "select item, scheduled from D" + timeinitid + "ou where initialed = '' and prescdr IS NULL and item != '';";
SqlDataAdapter sdyn = new SqlDataAdapter();
DataTable cpltTable = new DataTable();
cpltTable = GetData(pQuery);
gridviewschedcplt.DataSource = cpltTable;
gridviewschedcplt.DataBind();
con.Close();
}
else
{
return;
}
}
}
for (int j = 0; j < gridviewsched.Rows.Count; j++)
{
for (int i = 3; i < 9; i++)
{
gridviewsched.Rows[j].Cells[i].RowSpan = 2;
}
gridviewsched.Rows[j].Cells[2].RowSpan = 2;
}
}
private static DataTable GetData(string pQuery)
{
string schedtime;
string nowtime;
SqlDataAdapter sd1 = new SqlDataAdapter();
DataTable dTable = new DataTable();
using (SqlConnection conn = new SqlConnection("Data Source=localhost\\SQLEXPRESS;AttachDbFilename=C:\\Users\\Public\\public website\\slDataBase.mdf;Integrated Security=True;Trusted_Connection=True;MultipleActiveResultSets=True;"))
{
conn.Open();
SqlCommand cmd33 = new SqlCommand(pQuery, conn);
using (SqlDataReader reader99 = cmd33.ExecuteReader())
{
while (reader99.Read())
{
sd1.SelectCommand = cmd33;
***error here**** sd1.Fill(dTable);
DataRow newcpltTablerow = dTable.NewRow();
newcpltTablerow["item"] = reader99["item"].ToString();
dTable.Rows.Add(newcpltTablerow);
}
reader99.Close();
}
return dTable;
}
}

You do not need a SqlDataReader if you are using a SqldataAdapter. You are getting the error because you open a reader within an already open adapter. Do this instead (not compiled so tweak as needed and change the query to yours):
using (SqlConnection con = new SqlConnection(constring))
{
using (SqlCommand cmd = new SqlCommand("SELECT * FROM Customers", con))
{
cmd.CommandType = CommandType.Text;
using (SqlDataAdapter sda = new SqlDataAdapter(cmd))
{
using (DataTable dt = new DataTable())
{
sda.Fill(dt);
dataGridView1.DataSource = dt;
}
}
}
}

cmd33.ExecuteReader can only be called once. You are executing it for each row.

Return a object in C# [duplicate]

I have a database table with 3 columns firstname, Lastname and age. In my C# Windows application I have 3 textboxes called textbox1... I made my connectivity to my SQL Server using this code:
SqlConnection con = new SqlConnection("Data Source = .;
Initial Catalog = domain;
Integrated Security = True");
con.Open();
SqlCommand cmd = new SqlCommand("Select * from tablename", con);
I'd like to get values from my database; if I give a value in textbox1 it has to match the values in the database and retrieve other details to the corresponding textboxes.
I tried this method but it's not working:
cmd.CommandText = "select * from tablename where firstname = '" + textBox1.Text + "' ";
How can I do it to retrieve all the other values to the textboxes?

public Person SomeMethod(string fName)
{
var con = ConfigurationManager.ConnectionStrings["Yourconnection"].ToString();
Person matchingPerson = new Person();
using (SqlConnection myConnection = new SqlConnection(con))
{
string oString = "Select * from Employees where FirstName=#fName";
SqlCommand oCmd = new SqlCommand(oString, myConnection);
oCmd.Parameters.AddWithValue("#Fname", fName);
myConnection.Open();
using (SqlDataReader oReader = oCmd.ExecuteReader())
{
while (oReader.Read())
{
matchingPerson.firstName = oReader["FirstName"].ToString();
matchingPerson.lastName = oReader["LastName"].ToString();
}
myConnection.Close();
}
}
return matchingPerson;
}
Few things to note here: I used a parametrized query, which makes your code safer. The way you are making the select statement with the "where x = "+ Textbox.Text +"" part opens you up to SQL injection.
I've changed this to:
"Select * from Employees where FirstName=#fName"
oCmd.Parameters.AddWithValue("#fname", fName);
So what this block of code is going to do is:
Execute an SQL statement against your database, to see if any there are any firstnames matching the one you provided.
If that is the case, that person will be stored in a Person object (see below in my answer for the class).
If there is no match, the properties of the Person object will be null.
Obviously I don't exactly know what you are trying to do, so there's a few things to pay attention to: When there are more then 1 persons with a matching name, only the last one will be saved and returned to you.
If you want to be able to store this data, you can add them to a List<Person> .
Person class to make it cleaner:
public class Person
{
public string firstName { get; set; }
public string lastName { get; set; }
}
Now to call the method:
Person x = SomeMethod("John");
You can then fill your textboxes with values coming from the Person object like so:
txtLastName.Text = x.LastName;

create a class called DbManager:
Class DbManager
{
SqlConnection connection;
SqlCommand command;
public DbManager()
{
connection = new SqlConnection();
connection.ConnectionString = #"Data Source=. \SQLEXPRESS;AttachDbFilename=|DataDirectory|DatabaseName.mdf;Integrated Security=True;User Instance=True";
command = new SqlCommand();
command.Connection = connection;
command.CommandType = CommandType.Text;
} // constructor
public bool GetUsersData(ref string lastname, ref string firstname, ref string age)
{
bool returnvalue = false;
try
{
command.CommandText = "select * from TableName where firstname=#firstname and lastname=#lastname";
command.Parameters.Add("firstname",SqlDbType.VarChar).Value = firstname;
command.Parameters.Add("lastname",SqlDbType.VarChar).Value = lastname;
connection.Open();
SqlDataReader reader= command.ExecuteReader();
if (reader.HasRows)
{
while (reader.Read())
{
lastname = reader.GetString(1);
firstname = reader.GetString(2);
age = reader.GetString(3);
}
}
returnvalue = true;
}
catch
{ }
finally
{
connection.Close();
}
return returnvalue;
}
then double click the retrieve button(e.g btnretrieve) on your form and insert the following code:
private void btnretrieve_Click(object sender, EventArgs e)
{
try
{
string lastname = null;
string firstname = null;
string age = null;
DbManager db = new DbManager();
bool status = db.GetUsersData(ref surname, ref firstname, ref age);
if (status)
{
txtlastname.Text = surname;
txtfirstname.Text = firstname;
txtAge.Text = age;
}
}
catch
{
}
}

To retrieve data from database:
private SqlConnection Conn;
private void CreateConnection()
{
string ConnStr = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;
Conn = new SqlConnection(ConnStr);
}
public DataTable getData()
{
CreateConnection();
string SqlString = "SELECT * FROM TableName WHERE SomeID = #SomeID;";
SqlDataAdapter sda = new SqlDataAdapter(SqlString, Conn);
DataTable dt = new DataTable();
try
{
Conn.Open();
sda.Fill(dt);
}
catch (SqlException se)
{
throw;
}
catch (Exception ex)
{
throw;
}
finally
{
Conn.Close();
}
return dt;
}

You can use this simple method after setting up your connection:
private void getAgentInfo(string key)//"key" is your search paramter inside database
{
con.Open();
string sqlquery = "SELECT * FROM TableName WHERE firstname = #fName";
SqlCommand command = new SqlCommand(sqlquery, con);
SqlDataReader sReader;
command.Parameters.Clear();
command.Parameters.AddWithValue("#fName", key);
sReader = command.ExecuteReader();
while (sReader.Read())
{
textBoxLastName.Text = sReader["Lastname"].ToString(); //SqlDataReader
//["LastName"] the name of your column you want to retrieve from DB
textBoxAge.Text = sReader["age"].ToString();
//["age"] another column you want to retrieve
}
con.Close();
}
Now you can pass the key to this method by your textBoxFirstName like:
getAgentInfo(textBoxFirstName.Text);

we can use this type of snippet also we generally use this kind of code for testing and validating data for DB to API fields
class Db
{
private readonly static string ConnectionString =
ConfigurationManager.ConnectionStrings
["DbConnectionString"].ConnectionString;
public static List<string> GetValuesFromDB(string LocationCode)
{
List<string> ValuesFromDB = new List<string>();
string LocationqueryString = "select BELocationCode,CityLocation,CityLocationDescription,CountryCode,CountryDescription " +
$"from [CustomerLocations] where LocationCode='{LocationCode}';";
using (SqlConnection Locationconnection =
new SqlConnection(ConnectionString))
{
SqlCommand command = new SqlCommand(LocationqueryString, Locationconnection);
try
{
Locationconnection.Open();
SqlDataReader Locationreader = command.ExecuteReader();
while (Locationreader.Read())
{
for (int i = 0; i <= Locationreader.FieldCount - 1; i++)
{
ValuesFromDB.Add(Locationreader[i].ToString());
}
}
Locationreader.Close();
return ValuesFromDB;
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
throw;
}
}
}
}
hope this might helpful
Note: you guys need connection string (in our case
"DbConnectionString")

DataTable formerSlidesData = new DataTable();
DformerSlidesData = searchAndFilterService.SearchSlideById(ids[i]);
if (formerSlidesData.Rows.Count > 0)
{
DataRow rowa = formerSlidesData.Rows[0];
cabinet = Convert.ToInt32(rowa["cabinet"]);
box = Convert.ToInt32(rowa["box"]);
drawer = Convert.ToInt32(rowa["drawer"]);
}

How to retrieve data from a SQL Server database in C#?

I have a database table with 3 columns firstname, Lastname and age. In my C# Windows application I have 3 textboxes called textbox1... I made my connectivity to my SQL Server using this code:
SqlConnection con = new SqlConnection("Data Source = .;
Initial Catalog = domain;
Integrated Security = True");
con.Open();
SqlCommand cmd = new SqlCommand("Select * from tablename", con);
I'd like to get values from my database; if I give a value in textbox1 it has to match the values in the database and retrieve other details to the corresponding textboxes.
I tried this method but it's not working:
cmd.CommandText = "select * from tablename where firstname = '" + textBox1.Text + "' ";
How can I do it to retrieve all the other values to the textboxes?

public Person SomeMethod(string fName)
{
var con = ConfigurationManager.ConnectionStrings["Yourconnection"].ToString();
Person matchingPerson = new Person();
using (SqlConnection myConnection = new SqlConnection(con))
{
string oString = "Select * from Employees where FirstName=#fName";
SqlCommand oCmd = new SqlCommand(oString, myConnection);
oCmd.Parameters.AddWithValue("#Fname", fName);
myConnection.Open();
using (SqlDataReader oReader = oCmd.ExecuteReader())
{
while (oReader.Read())
{
matchingPerson.firstName = oReader["FirstName"].ToString();
matchingPerson.lastName = oReader["LastName"].ToString();
}
myConnection.Close();
}
}
return matchingPerson;
}
Few things to note here: I used a parametrized query, which makes your code safer. The way you are making the select statement with the "where x = "+ Textbox.Text +"" part opens you up to SQL injection.
I've changed this to:
"Select * from Employees where FirstName=#fName"
oCmd.Parameters.AddWithValue("#fname", fName);
So what this block of code is going to do is:
Execute an SQL statement against your database, to see if any there are any firstnames matching the one you provided.
If that is the case, that person will be stored in a Person object (see below in my answer for the class).
If there is no match, the properties of the Person object will be null.
Obviously I don't exactly know what you are trying to do, so there's a few things to pay attention to: When there are more then 1 persons with a matching name, only the last one will be saved and returned to you.
If you want to be able to store this data, you can add them to a List<Person> .
Person class to make it cleaner:
public class Person
{
public string firstName { get; set; }
public string lastName { get; set; }
}
Now to call the method:
Person x = SomeMethod("John");
You can then fill your textboxes with values coming from the Person object like so:
txtLastName.Text = x.LastName;

create a class called DbManager:
Class DbManager
{
SqlConnection connection;
SqlCommand command;
public DbManager()
{
connection = new SqlConnection();
connection.ConnectionString = #"Data Source=. \SQLEXPRESS;AttachDbFilename=|DataDirectory|DatabaseName.mdf;Integrated Security=True;User Instance=True";
command = new SqlCommand();
command.Connection = connection;
command.CommandType = CommandType.Text;
} // constructor
public bool GetUsersData(ref string lastname, ref string firstname, ref string age)
{
bool returnvalue = false;
try
{
command.CommandText = "select * from TableName where firstname=#firstname and lastname=#lastname";
command.Parameters.Add("firstname",SqlDbType.VarChar).Value = firstname;
command.Parameters.Add("lastname",SqlDbType.VarChar).Value = lastname;
connection.Open();
SqlDataReader reader= command.ExecuteReader();
if (reader.HasRows)
{
while (reader.Read())
{
lastname = reader.GetString(1);
firstname = reader.GetString(2);
age = reader.GetString(3);
}
}
returnvalue = true;
}
catch
{ }
finally
{
connection.Close();
}
return returnvalue;
}
then double click the retrieve button(e.g btnretrieve) on your form and insert the following code:
private void btnretrieve_Click(object sender, EventArgs e)
{
try
{
string lastname = null;
string firstname = null;
string age = null;
DbManager db = new DbManager();
bool status = db.GetUsersData(ref surname, ref firstname, ref age);
if (status)
{
txtlastname.Text = surname;
txtfirstname.Text = firstname;
txtAge.Text = age;
}
}
catch
{
}
}

To retrieve data from database:
private SqlConnection Conn;
private void CreateConnection()
{
string ConnStr = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;
Conn = new SqlConnection(ConnStr);
}
public DataTable getData()
{
CreateConnection();
string SqlString = "SELECT * FROM TableName WHERE SomeID = #SomeID;";
SqlDataAdapter sda = new SqlDataAdapter(SqlString, Conn);
DataTable dt = new DataTable();
try
{
Conn.Open();
sda.Fill(dt);
}
catch (SqlException se)
{
throw;
}
catch (Exception ex)
{
throw;
}
finally
{
Conn.Close();
}
return dt;
}

You can use this simple method after setting up your connection:
private void getAgentInfo(string key)//"key" is your search paramter inside database
{
con.Open();
string sqlquery = "SELECT * FROM TableName WHERE firstname = #fName";
SqlCommand command = new SqlCommand(sqlquery, con);
SqlDataReader sReader;
command.Parameters.Clear();
command.Parameters.AddWithValue("#fName", key);
sReader = command.ExecuteReader();
while (sReader.Read())
{
textBoxLastName.Text = sReader["Lastname"].ToString(); //SqlDataReader
//["LastName"] the name of your column you want to retrieve from DB
textBoxAge.Text = sReader["age"].ToString();
//["age"] another column you want to retrieve
}
con.Close();
}
Now you can pass the key to this method by your textBoxFirstName like:
getAgentInfo(textBoxFirstName.Text);

we can use this type of snippet also we generally use this kind of code for testing and validating data for DB to API fields
class Db
{
private readonly static string ConnectionString =
ConfigurationManager.ConnectionStrings
["DbConnectionString"].ConnectionString;
public static List<string> GetValuesFromDB(string LocationCode)
{
List<string> ValuesFromDB = new List<string>();
string LocationqueryString = "select BELocationCode,CityLocation,CityLocationDescription,CountryCode,CountryDescription " +
$"from [CustomerLocations] where LocationCode='{LocationCode}';";
using (SqlConnection Locationconnection =
new SqlConnection(ConnectionString))
{
SqlCommand command = new SqlCommand(LocationqueryString, Locationconnection);
try
{
Locationconnection.Open();
SqlDataReader Locationreader = command.ExecuteReader();
while (Locationreader.Read())
{
for (int i = 0; i <= Locationreader.FieldCount - 1; i++)
{
ValuesFromDB.Add(Locationreader[i].ToString());
}
}
Locationreader.Close();
return ValuesFromDB;
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
throw;
}
}
}
}
hope this might helpful
Note: you guys need connection string (in our case
"DbConnectionString")

DataTable formerSlidesData = new DataTable();
DformerSlidesData = searchAndFilterService.SearchSlideById(ids[i]);
if (formerSlidesData.Rows.Count > 0)
{
DataRow rowa = formerSlidesData.Rows[0];
cabinet = Convert.ToInt32(rowa["cabinet"]);
box = Convert.ToInt32(rowa["box"]);
drawer = Convert.ToInt32(rowa["drawer"]);
}

MultipleActiveResultSets enabled but not working

I enabled MARS and still cant execute two SqlDataReaders in one connection,i searched for a solution to enable MARS by default using RegEdit by couldnt find any solution and still getting that error : There is already an open DataReader associated with this Command which must be closed first.
Here is the code :
public partial class student_Courses : System.Web.UI.Page
{
string connectionString = "";
string query1 = "";
string query2 = "";
string courseName = "";
string chapterName = "";
string chapterVideoName = "";
string courseValue = "";
SqlDataReader sr2 = null;
protected void Page_Load(object sender, EventArgs e)
{
query1 = "SELECT * FROM Courses";
query2 = "SELECT * FROM Chapters WHERE value='" + courseValue + "'";
connectionString = "Data Source=Prince-PC;" +
"Initial Catalog=Elearning;" +
"Integrated Security=True;"+
"MultipleActiveResultSets=True";
SqlConnection con = new SqlConnection(connectionString);
SqlCommand command1 = new SqlCommand(query1, con);
SqlCommand command2 = new SqlCommand(query2, con);
if (con.State == ConnectionState.Closed)
con.Open();
using (SqlDataReader sr1 = command1.ExecuteReader())
{
while (sr1.Read())
{
courseName = sr1["name"].ToString();
courseValue = sr1["value"].ToString();
sr2 = command2.ExecuteReader();
while (sr2.Read())
{
chapterName = TextBox3.Text = sr2["name"].ToString();
chapterVideoName = Label2.Text = sr2["video_name"].ToString();
}
}
}
con.Close();
}
}

You need to dispose of sr2 via a using statement as done in this MSDN MARS example
// The following line of code requires
// a MARS-enabled connection.
productReader = productCmd.ExecuteReader();
using (productReader)
{
while (productReader.Read())
{
Console.WriteLine(" " +
productReader["Name"].ToString());
}
}