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Return results from SQL query in a specific format [duplicate]

I'm trying to get data from a SQL Server database and return data (all data) based on a query as follows:
public async Task<List<PersonEntity>> GetDataAsync()
{
var allUsers = new List<PersonEntity>();
SqlConnection conn = new SqlConnection("");
conn.Open();
SqlCommand cmd = new SqlCommand("Select* from <TABLE> <WHERE>", conn);
SqlDataReader reader = cmd.ExecuteReader();
if (reader.HasRows)
{
while (reader.Read())
{
var a = new PersonEntity {
LocationAreaCode = reader.GetString(0),
PersonStatusCode = reader.GetString(1),
PersonStatusDesc = reader.GetString(2)
};
allUsers.Add(a);
}
}
else
{
// no data found
}
reader.Close();
conn.Close();
return allUsers;
}
Is there a better way (in terms of performance) to read all data (values from all the columns) matching the query and return the data from this function?

You need to use ADO.net SqlDataAdapter Class
var ds = new DataSet();
using (SqlConnection connection = new SqlConnection(connectionString)) {
connection.Open();
var command = connection.CreateCommand();
command.CommandText = "Select * from <table-name> where location = 'US'";
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(ds);
}

C# MySqlConnector next query in the same connection

I have the following code:
string myConnection = "server=localhost;database=test;uid=test;password=test";
string query = "SELECT label_type, label, quantity FROM system_printserver WHERE print=0";
try
{
MySqlConnection myConn = new MySqlConnection(myConnection);
myConn.Open();
MySqlCommand command = new MySqlCommand(query, myConn);
MySqlDataAdapter adapter = new MySqlDataAdapter(command);
DataTable data = new DataTable();
adapter.Fill(data);
dataGridView1.DataSource = data;
printDocument1.PrintPage += new PrintPageEventHandler(printDocument1_PrintPage);
MySqlDataReader myReader;
myReader = command.ExecuteReader();
while (myReader.Read()) {
orderNumber = myReader.GetString(1);
myReader.Close();
string queryOrder = "SELECT id_order, id_carrier FROM ps_orders WHERE id_order=28329";
MySqlCommand commandOrder = new MySqlCommand(queryOrder, myConn);
MySqlDataReader myReaderOrder;
myReaderOrder = commandOrder.ExecuteReader();
idCarrier = myReaderOrder.GetString(1);
printDocument1.Print();
}
I have a problem because the second query string queryOrder doesn't work. The query is Ok but variable "idCarrier" doesn't accept any value.

I don't believe you can attach another reader to a connection, when one is already open and processing records. You must retrieve all your records first, i.e. ToList() or Dataset, or use a secondary connection for the second reader.
To make your life easier, consider using Dapper or Linq2Db, two awesome micro-ORMs.

Try it like this:
using(var connection = new MySqlConnection("server=localhost;database=test;uid=test;password=test") {
connection.Open();
int orderNumber = 0;
using (var command = connection.CreateCommand()) {
command.CommandText = #"SELECT label_type, label, quantity FROM system_printserver WHERE print=0";
DataTable data = new DataTable();
adapter.Fill(data);
dataGridView1.DataSource = data;
var reader = command.ExecuteReader();
printDocument1.PrintPage += new PrintPageEventHandler(printDocument1_PrintPage);
if(reader.Read()) {
orderNumber = Convert.ToInt32(reader.GetString(1));
}
}
using(var command = connection.CreateCommand()) {
command.CommandText = string.format(#"SELECT id_order, id_carrier FROM ps_orders WHERE id_order={0}",orderNumber);
var reader = command.ExecuteReader();
if(reader.Read()){
printDocument1.Print();
return reader.GetString(1);
}
}
}

How can I get SQL result into a STRING variable?

I'm trying to get the SQL result in a C# string variable or string array. Is it possible? Do I need to use SqlDataReader in some way?
I'm very new to C# functions and all, used to work in PHP, so please give a working example if you can (If relevant I can already connect and access the database, insert and select.. I just don't know how to store the result in a string variable).

This isn't the single greatest example in history, as if you don't return any rows from the database you'll end up with an exception, but if you want to use a stored procedure from the database, rather than running a SELECT statement straight from your code, then this will allow you to return a string:
public string StringFromDatabase()
{
SqlConnection connection = null;
try
{
var dataSet = new DataSet();
connection = new SqlConnection("Your Connection String Goes Here");
connection.Open();
var command = new SqlCommand("Your Stored Procedure Name Goes Here", connection)
{
CommandType = CommandType.StoredProcedure
};
var dataAdapter = new SqlDataAdapter { SelectCommand = command };
dataAdapter.Fill(dataSet);
return dataSet.Tables[0].Rows[0]["Item"].ToString();
}
catch (Exception ex)
{
throw new Exception(ex.Message, ex);
}
finally
{
if (connection != null)
{
connection.Close();
}
}
}
It can definitely be improved, but it would give you a starting point to work from if you want to go down a stored procedure route.

Try This:
SqlConnection con=new SqlConnection("/*connection string*/");
SqlCommand SelectCommand = new SqlCommand("SELECT email FROM table1", con);
SqlDataReader myreader;
con.Open();
myreader = SelectCommand.ExecuteReader();
List<String> lstEmails=new List<String>();
while (myreader.Read())
{
lstEmails.Add(myreader[0].ToString());
//strValue=myreader["email"].ToString();
//strValue=myreader.GetString(0);
}
con.Close();
accessing the Emails from list
lstEmails[0]->first email
lstEmails[1]->second email
...etc.,

You could use an SQL Data Reader:
string sql = "SELECT email FROM Table WHERE Field = #Parameter";
string variable;
using (var connection = new SqlConnection("Your Connection String"))
using (var command = new SqlCommand(sql, connection))
{
command.Parameters.AddWithValue("#Parameter", someValue);
connection.Open();
using (var reader = command.ExecuteReader())
{
//Check the reader has data:
if (reader.Read())
{
variable = reader.GetString(reader.GetOrdinal("Column"));
}
// If you need to use all rows returned use a loop:
while (reader.Read())
{
// Do something
}
}
}
Or you could use SqlCommand.ExecuteScalar()
string sql = "SELECT email FROM Table WHERE Field = #Parameter";
string variable;
using (var connection = new SqlConnection("Your Connection String"))
using (var command = new SqlCommand(sql, connection))
{
command.Parameters.AddWithValue("#Parameter", someValue);
connection.Open();
variable = (string)command.ExecuteScalar();
}

This May help you For MySQL
MySqlDataReader reader = mycommand.ExecuteReader();
while (reader.Read())
{
TextBox2.Text = reader.ToString();
}
For SQL
using (SqlCommand command = new SqlCommand("*SELECT QUERY HERE*", connection))
{
//
// Invoke ExecuteReader method.
//
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
TextBox2.Text = reader.GetString(0);
}
}

Try this:
public string SaveStringSQL(string pQuery, string ConnectionString)
{
var connection = new Conexao(ConnectionString);
connection.Open();
SqlCommand command = new SqlCommand(pQuery, connection.Connection);
var SavedString = (string)command.ExecuteScalar();
connection.Close();
return SavedString;
}
The ExecuteScalar function saves whatever type of data there is on your database - you just have to specify it.
Keep in mind that it can only save one line at a time.

How to get list of all database from sql server in a combobox using c#.net

I am entering the source name userid and password through the textbox and want the database list should be listed on the combo box so that all the four options sourcename, userid, password and databasename can be selected by the user to perform the connectivity
The databases are to be retrieve from other system as per the user. User will enter the IP, userid and password and they should get the database list in the combo box so that they can select the required database and perform the connectivity
private void frmConfig_Load(object sender, EventArgs e)
{
try
{
string Conn = "server=servername;User Id=userid;" + "pwd=******;";
con = new SqlConnection(Conn);
con.Open();
da = new SqlDataAdapter("SELECT * FROM sys.database", con);
cbSrc.Items.Add(da);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
I am trying to do this but it is not generating any data

sys.databases
SELECT name
FROM sys.databases;
Edit:
I recommend using IDataReader, returning a List and caching the results. You can simply bind your drop down to the results and retrieve the same list from cache when needed.
public List<string> GetDatabaseList()
{
List<string> list = new List<string>();
// Open connection to the database
string conString = "server=xeon;uid=sa;pwd=manager; database=northwind";
using (SqlConnection con = new SqlConnection(conString))
{
con.Open();
// Set up a command with the given query and associate
// this with the current connection.
using (SqlCommand cmd = new SqlCommand("SELECT name from sys.databases", con))
{
using (IDataReader dr = cmd.ExecuteReader())
{
while (dr.Read())
{
list.Add(dr[0].ToString());
}
}
}
}
return list;
}

First add following assemblies:
Microsoft.SqlServer.ConnectionInfo.dll
Microsoft.SqlServer.Management.Sdk.Sfc.dll
Microsoft.SqlServer.Smo.dll
from
C:\Program Files\Microsoft SQL Server\100\SDK\Assemblies\
and then use below code:
var server = new Microsoft.SqlServer.Management.Smo.Server("Server name");
foreach (Database db in server.Databases) {
cboDBs.Items.Add(db.Name);
}

you can use on of the following queries:
EXEC sp_databases
SELECT * FROM sys.databases
Serge

Simply using GetSchema method:
using (SqlConnection connection = GetConnection())
{
connection.Open();
DataTable dtDatabases = connection.GetSchema("databases");
//Get database name using dtDatabases["database_name"]
}

using (var connection = new System.Data.SqlClient.SqlConnection("ConnectionString"))
{
connection.Open();
var command = new System.Data.SqlClient.SqlCommand();
command.Connection = connection;
command.CommandType = CommandType.Text;
command.CommandText = "SELECT name FROM master.sys.databases";
var adapter = new System.Data.SqlClient.SqlDataAdapter(command);
var dataset = new DataSet();
adapter.Fill(dataset);
DataTable dtDatabases = dataset.Tables[0];
}

How to get list of all database from sql server in a combobox using c# asp.net windows application
try
{
string Conn = "server=.;User Id=sa;" + "pwd=passs;";
SqlConnection con = new SqlConnection(Conn);
con.Open();
SqlCommand cmd = new SqlCommand();
// da = new SqlDataAdapter("SELECT * FROM sys.database", con);
cmd = new SqlCommand("SELECT name FROM sys.databases", con);
// comboBox1.Items.Add(cmd);
SqlDataReader dr;
dr = cmd.ExecuteReader();
if (dr.HasRows)
{
while (dr.Read())
{
//comboBox2.Items.Add(dr[0]);
comboBox1.Items.Add(dr[0]);
}
}
// .Items.Add(da);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}

Try this:
SqlConnection con = new SqlConnection(YourConnectionString);
SqlCommand cmd = new SqlCommand("SELECT name from sys.databases", con);
con.Open();
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
cbSrc.Items.Add(dr[0].ToString());
}
con.Close();
or this:
DataSet ds = new DataSet();
SqlDataAdapter sqlda = new SqlDataAdapter("SELECT name from sys.databases", YourConnectionString);
sqlda.Fill(ds);
for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
{
cbSrc.Items.Add(ds.Tables[0].Rows[i][0].ToString());
}

public static List<string> GetAllDatabaseNamesByServerName(string ServerName, [Optional] string UserID, [Optional] string Password)
{
List<string> lstDatabaseNames = null;
try
{
lstDatabaseNames = new List<string>();
//string servername = System.Environment.MachineName;
string newConnString = string.Format("Data Source={0};", ServerName);
if (UserID == null)
{
newConnString += "Integrated Security = True;";
}
else
{
newConnString += string.Format("User Id ={0}; Password={1};", UserID, Password);
}
SqlConnection con = new SqlConnection(newConnString);
con.Open();
SqlCommand cmd = new SqlCommand("SELECT name FROM master.sys.databases", con);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
foreach (DataRow row in dt.Rows)
{
lstDatabaseNames.Add(row[0].ToString());
}
con.Close();
return lstDatabaseNames;
}
finally
{
}
}

How can I retrieve a table from stored procedure to a datatable?

I created a stored procedure so as to return me a table.
Something like this:
create procedure sp_returnTable
body of procedure
select * from table
end
When I call this stored procedure on the frontend what code do I need to write to retrieve it in a datatable object?
I wrote code something like the following. I basically want to know retrieving and storing table into an object of datatable. All my queries are running, but I don't know how to retrieve table into a datatable through a stored procedure
DataTable dtable = new DataTable();
cmd.Connection = _CONN;
cmd.CommandText = SPNameOrQuery;
cmd.CommandType = CommandType.StoredProcedure;
SqlDataAdapter adp = new SqlDataAdapter(cmd);
OpenConnection();
adp.Fill(dtTable);
CloseConnection();
Here in this code a command has been bound with the stored procedure name and its parameters. Will it be returning me a datatable from the stored procedure?

string connString = "<your connection string>";
string sql = "name of your sp";
using(SqlConnection conn = new SqlConnection(connString))
{
try
{
using(SqlDataAdapter da = new SqlDataAdapter())
{
da.SelectCommand = new SqlCommand(sql, conn);
da.SelectCommand.CommandType = CommandType.StoredProcedure;
DataSet ds = new DataSet();
da.Fill(ds, "result_name");
DataTable dt = ds.Tables["result_name"];
foreach (DataRow row in dt.Rows) {
//manipulate your data
}
}
}
catch(SQLException ex)
{
Console.WriteLine("SQL Error: " + ex.Message);
}
catch(Exception e)
{
Console.WriteLine("Error: " + e.Message);
}
}
Modified from Java Schools Example

Set the CommandText as well, and call Fill on the SqlAdapter to retrieve the results in a DataSet:
var con = new SqlConnection();
con.ConnectionString = "connection string";
var com = new SqlCommand();
com.Connection = con;
com.CommandType = CommandType.StoredProcedure;
com.CommandText = "sp_returnTable";
var adapt = new SqlDataAdapter();
adapt.SelectCommand = com;
var dataset = new DataSet();
adapt.Fill(dataset);
(Example is using parameterless constructors for clarity; can be shortened by using other constructors.)

Explaining if any one want to send some parameters while calling stored procedure as below,
using (SqlConnection con = new SqlConnection(connetionString))
{
using (var command = new SqlCommand(storedProcName, con))
{
foreach (var item in sqlParams)
{
item.Direction = ParameterDirection.Input;
item.DbType = DbType.String;
command.Parameters.Add(item);
}
command.CommandType = CommandType.StoredProcedure;
using (var adapter = new SqlDataAdapter(command))
{
adapter.Fill(dt);
}
}
}