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Can't select numerical values from database into a TextBox

I want to use a combobox to retrieve data from an access database, but it doesn't work with numerical values.
This part of the code is the connection string and object:
public partial class StockControl : Form
{
OleDbConnection connection = new OleDbConnection();
public StockControl()
{
InitializeComponent();
connection.ConnectionString = #"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Folder\NewStockControl.mdb;Persist Security Info=False;";
}
Here is the code I used to retrieve the field ProductName in the Access database (StockControl is the name of the form I created):
private void StockControl_Load(object sender, EventArgs e)
{
try
{
connection.Open();
OleDbCommand command = new OleDbCommand();
command.Connection = connection;
string query = "select ProductName from Products";
command.CommandText = query;
OleDbDataReader reader = command.ExecuteReader();
while (reader.Read())
{
cbProductId.Items.Add(reader["ProductName"].ToString());
}
connection.Close();
}
catch (Exception ex)
{
MessageBox.Show("Error" + ex);
}
}
And here is the code I added to the combo box (cbProductId)
private void cbProductId_SelectedIndexChanged(object sender, EventArgs e)
{
try
{
connection.Open();
OleDbCommand command = new OleDbCommand();
command.CommandType = CommandType.Text;
command.Connection = connection;
string query = "SELECT * from Products WHERE ProductName='"+cbProductId.Text+"'";
command.CommandText = query;
OleDbDataReader reader = command.ExecuteReader();
while (reader.Read())
{
txtStockName.Text = reader["ProductName"].ToString();
txtStockQty.Text= reader["SupplyLeft"].ToString();
}
connection.Close();
}
catch (Exception ex)
{
MessageBox.Show("Error" + ex);
}
}
There are two textboxes in the StockControl form: txtStockName and txtStockQty, and I want the fields ProductName and SupplyLeft to be displayed in those textboxes respectively. However whenever I run the code the only value that shows is ProductName, but SupplyLeft doesn't. I assume it has to do with the fact that it is an integer rather than a string, but I don't know how to convert the text box to be able to display the value SupplyLeft.

how to retrieve data from database in combobox c#

I wrote this code but I do not know why this line gives error!
String sname = dr.GetString ("name");
My code:
SqlConnection cn = new SqlConnection(
"Data Source=.;Initial Catalog=logindb;Integrated Security=True");
string query1 = "select * from tbllogin";
SqlCommand cmd = new SqlCommand(query1);
SqlDataReader dr;
try
{
cn.Open();
dr = cmd.ExecuteReader();
while (dr.Read())
{
String sname = dr.GetString("name");
comboBox1.Items.Add(sname);
}
}
catch (Exception e)
{
// do smth about exception
}

First of all you have to check this again:
SqlConnection cn = new SqlConnection(
"Data Source=.;Initial Catalog=logindb;Integrated Security=True");
Data Source=.; This is wrong and it will give you an error.
After that you can use the code below to achieve what you want. The code below also uses using statement to dispose the connection.
using (
SqlConnection connection = new SqlConnection(strCon)) // strCon is the string containing connection string
{
SqlCommand command = new SqlCommand("select * from tbllogin", connection);
connection.Open();
DataReader reader = command.ExecuteReader();
if (reader.HasRows)
{
while (reader.Read())
{
comboBox1.Items.Add(reader.GetString(int index)); // index of column you want, because this method takes only int
}
}
reader.Close();
}

(Amazingly) GetString only take an index as parameter.
See MSDN
public override string GetString(int i)
With no other signatures :-(
However you could write:
String sname = dr.Item["name"].ToString();

MSDN says that SqlDataReader.GetString method accepts an int as a parameter, which is the index of the column.
What you need is this:
while (dr.Read())
{
String sname = (string)dr["name"];
comboBox1.Items.Add(sname);
}
Here's your code:
SqlConnection cn = new SqlConnection("Data Source=.;Initial Catalog=logindb;Integrated Security=True");
string query1 = "select * from tbllogin"; SqlCommand cmd = new SqlCommand(query1); SqlDataReader dr;
try {
cn.Open(); dr = cmd.ExecuteReader();
while (dr.Read())
{ String sname = (string)dr["name"];
comboBox1.Items.Add(sname);
}
}
catch (Exception e) { MessageBox.Show(e.Message, "An error occurred!"); }
The catch block wasn't written correctly, you missed the (Exception e) part.

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.

Checking condition which table to Insert

I want to Check the "refno" already present in Tbldelivery table, If "refno" is present, then it will insert in "Tbldeliverydetails" because "refno" is primary key in 1st table. Where i check the condition ?
Here is the code i wrote in C# :
protected void btndlysave_Click(object sender, EventArgs e)
{
SqlConnection SqlCon = new SqlConnection("server=(local);Initial Catalog=TestDB;Integrated Security=SSPI;");
try
{
SqlCon.Open();
SqlCommand cmd = new SqlCommand("insert into Tbldelivery (refno,deliverdate,requestby,projectcode) values
(#refno,#deliverdate,#requestby,#projectcode) WHERE not exists (select refno from Tblinkdelivery where refno = #refno)", SqlCon);
cmd.CommandType = CommandType.Text;
if ( need check here)
cmd.Parameters.AddWithValue("#refno", txtdelrefno.Text.Trim());
cmd.Parameters.AddWithValue("#deliverdate", txtdeldate.Text.Trim());
cmd.Parameters.AddWithValue("#requestby", txtdelreq.Text.Trim());
cmd.Parameters.AddWithValue("#projectcode", ddlprojcode.Text.Trim());
}
else
{
SqlCommand cmd2 = new SqlCommand("insert into Tbldeliverdetails (refno,printercode,inkcode,quantity,price,notes) values (#refno,#printercode,#inkcode,#quantity,#price,#notes)", SqlCon);
cmd2.CommandType = CommandType.Text;
cmd2.Parameters.AddWithValue("#refno", txtdelrefno.Text.Trim());
cmd2.Parameters.AddWithValue("#printercode", ddldelprcode.Text.Trim());
cmd2.Parameters.AddWithValue("#inkcode", ddlinkcode.Text.Trim());
cmd2.Parameters.AddWithValue("#quantity", txtdelqty.Text.Trim());
cmd2.Parameters.AddWithValue("#price", txtdelprice.Text.Trim());
cmd2.Parameters.AddWithValue("#notes", txtdelnotes.Text.Trim());
int val1 = cmd.ExecuteNonQuery();
int val2 = cmd2.ExecuteNonQuery();
}
finally
{
SqlCon.Close();
}
}

I think first of all you need to arrange your code.
Writing everything inside the button click event is not good at all. It is better if you can separate business logic and put it separately.
Try something like this.
You can create Data Access class which handle your data access.
In your Data Access Class
public SqlConnection OpenConnection()
{
try
{
var conn = new SqlConnection(“xxx”);
conn.Open();
return conn;
}
catch (Exception ex)
{
//log the exception
return null;
}
}
YourFunction(parameters)
{
var conn = OpenConnection();
if(conn != null)
{
//your code
// you can do something similar as JeremyK explained here
}
}
And in your button click
protected void btndlysave_Click(object sender, EventArgs e)
{
//CHECK THE PARAMETERS AND PASS
//DataAccess. YourFunction(parameters)
}

You query the table and see if it exists.
using (SqlConnection connection = new SqlConnection(connectionString))
{
connection.Open();
SqlCommand sqlCommand =
new SqlCommand("SELECT * FROM dbo.Tbldelivery WHERE refno=#refno",
connection);
sqlCommand.Parameters.Add("#refno", System.Data.SqlDbType.VarChar);
sqlCommand.Parameters["#refno"].Value = refnoValue;
SqlDataReader reader = sqlCommand.ExecuteReader();
reader.Read();
if (reader.HasRows)
{
// refno exists
}
else
{
// refno does not exist
}
}

How to bind a datasource to a label control

It's easy to bind a data source to something like a gridview or repeater, but how would I do it with a label? Heres the sql connection that I want to modify. By the way, I don't need 2 way binding.
public void Sql_Connection(string queryString)
{
SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["RBConnectionString"].ConnectionString);
SqlCommand cmd = new SqlCommand(queryString, conn);
conn.Open();
cmd.ExecuteNonQuery();
conn.Close();
}
The query I'm using:
SELECT Description FROM RbSpecials WHERE Active=1

public string SqlConnection(string queryString)
{
using (var conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["RBConnectionString"].ConnectionString))
using (var cmd = conn.CreateCommand())
{
conn.Open();
cmd.CommandText = queryString;
using (var reader = cmd.ExecuteReader())
{
while (reader.Read())
{
// This will return the first result
// but there might be other
return reader.GetString(0);
}
}
return null;
}
}
This will also ensure that in case of exception all disposable objects are disposed and will properly return the SQLConnection to the connection pool in order to be reused.
And finally assign the Text property of the label:
lblTest.Text = SqlConnection("SELECT Description FROM RbSpecials WHERE Active=1");

use ExecuteReader rather than ExecuteNonQuery
public void Sql_Connection(string queryString)
{
using(SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings"RBConnectionString"].ConnectionString))
{
using(SqlCommand cmd = new SqlCommand(queryString, conn))
{
conn.Open();
using(SqlDataReader rdr = cmd.ExecuteReader())
{
while(rdr.Read())
{
lblDescription.Text = rdr.GetString(0);
}
}
}
}
}

using (SqlConnection con = new SqlConnection(Connection_String))
{
SqlCommand cmd = new SqlCommand("select * from Customers", con);
cmd.CommandType = CommandType.StoredProcedure;
SqlDataReader adpt = cmd.ExecureReader();
if(rdr.Read())
{
lblName.Text = rdr[0].ToString();
}
}