Develop Reference

How to Query Return Value on using Compact SQL Command?

I using a compact database created on visual studio. just for a stand alone system with it's database intact already although i'm stuck here in using a select query that could retrieve a boolean if the user exist on the database and also then return it's ID and Username if the user entry exist. can i ask for help regarding on this one.. I am a student trying to learn c# on using compact database.
private void btnLogin_Click(object sender, EventArgs e)
{
try
{
if (!IsEmpty())
{
if (!IsLenght())
{
using (SqlCeConnection con = new SqlCeConnection("Data Source=" +
System.IO.Path.Combine(Path.GetDirectoryName(System.Reflection.Assembly.GetEntryAssembly().Location), "INCdb.sdf")))
{
con.Open();
SqlCeCommand cmd = con.CreateCommand();
cmd.CommandText = "SELECT * FROM LoginTB Where username=#user1 AND password=#pass1";
cmd.Parameters.AddWithValue("#user1", UserTxt.Text.Trim());
cmd.Parameters.AddWithValue("#pass1", PassTxt.Text.Trim());
cmd.CommandType = CommandType.Text;
validlogin = (bool)cmd.ExecuteScalar();
con.Close();
MessageBox.Show(validlogin.ToString());
if (validlogin == true)
{
// cmd. return value ID
// cmd. return value Username
//SysMain Mn = new SysMain();
//Mn.ShowDialog();
//this.Hide();
}
}
}
}
}
catch (Exception ex)
{
gbf.msgBox(1, ex.Message.ToString(), "");
}
}

The code below is probably better, unless there is something special and unstated about the schema of LoginTB.
// ...
var validLogin = false;
using (SqlCeConnection con = new SqlCeConnection(
"Data Source=" +
System.IO.Path.Combine(
Path.GetDirectoryName(
System.Reflection.Assembly.GetEntryAssembly().Location),
"INCdb.sdf")))
{
con.Open();
SqlCeCommand cmd = con.CreateCommand();
cmd.CommandText =
"SELECT COUNT(*) FROM LoginTB Where username=#user1 AND password=#pass1";
cmd.Parameters.AddWithValue("#user1", UserTxt.Text.Trim());
cmd.Parameters.AddWithValue("#pass1", PassTxt.Text.Trim());
cmd.CommandType = CommandType.Text;
validlogin = ((int)cmd.ExecuteScalar()) > 0;
}
MessageBox.Show(validlogin.ToString());
// ...
Note the use of COUNT

C# project runs with no errors but doesn't add anything in the database?

I am trying to add records into my C# project and it runs with no errors but it doesn't add anything in the database:
private void saveBtn_Click(object sender, EventArgs e)
{
if (admNo.Text != "" & session.Text != "" & name.Text != "")
{
SqlConnection cn = new SqlConnection("Data Source=C:\\Users\\Divya Pathak\\Documents\\Visual Studio 2012\\Projects\\SchoolRecord\\SchoolRecord\\Database1.sdf");
SqlCommand cmd = new SqlCommand();
cn.Open();
cmd.CommandText = "insert into addNew (no,session,name) values ('" + admNo.Text + "', '" + session.Text + "', '" + name.Text + "')";
cmd.ExecuteNonQuery();
cn.Close();
MessageBox.Show("Record inserted successfully", "mission successfull");
}
}
Could someone please advise why?

you need to set cm.Connection as cn
cm.Connection =cn;
OR
using (var cn = new SqlCeConnection("connection string"))
using (var cmd = new SqlCeCommand("insert addNew (no,session,name) values (#no,#session,#name)", cn))
{
cmd.Parameters.AddWithValue("#no", admNo.Text);
cmd.Parameters.AddWithValue("#session", session.Text);
cmd.Parameters.AddWithValue("#name", name.Text);
cn.Open();
cmd.ExecuteNonQuery();
}
This will help you to write the correct connection string for SQL CE

You have four mistakes:
You never associate the connection with the command
You're connecting to a Sql Server Compact database using the full Sql Server provider (you should be using the SqlCe namespace:
You're building your query using unsafe string concatenation instead of query parameters. Fix this!
Your connection won't be closed if an exception is thrown, which can ultimately lock you out of your database. You need to close the connection as part of a finally block, and the easiest way to do this is with a using block.
.
using (var cn = new SqlCeConnection("connection string here"))
using (var cmd = new SqlCeCommand("insert into addNew (no,session,name) values (#no,#session,#name)", cn))
{
//guessing at column lengths:
cmd.Parameters.Add("#no", SqlDbType.Int).Value = int.Parse(admNo.Text);
cmd.Parameters.Add("#session", SqlDbType.NVarChar, 100).Value = session.Text;
cmd.Parameters.Add("#name", SqlDbType.NVarChar, 60).Value = name.Text;
cn.Open();
cmd.ExecuteNonQuery();
}

error for insert and stored data in access 2013

i have this code for insert data into access 2013
after click in the save button data insert into dataGridView and show
and when stop program and restart this,data not stored in the DB.I've done a lot of searches but can't find the solution. my class code and my button save code
class DB
{
public static OleDbConnection con = new OleDbConnection();
static DB()
{
con.ConnectionString = "Provider=MICROSOFT.ACE.OLEDB.12.0; " +
"Data Source=|DataDirectory|//Phonebook-db.accdb;Persist Security Info=True";
}
public static void Insert(Person p1)
{
try
{
OleDbCommand cmd = con.CreateCommand();
con.Open();
string s = "INSERT INTO Industrialist (S_Name,S_Family,S_Telephone,S_Major)VALUES('" + p1.Name + "','" + p1.Family + "','" + p1.Telephone + "','" + p1.Major + "')";
cmd.CommandType = CommandType.Text;
cmd.CommandText = s;
cmd.ExecuteNonQuery();
con.Close();
System.Windows.Forms.MessageBox.Show("Record successfully Added");
}
catch (OleDbException exp) { MessageBox.Show(exp.ToString()); }
}
}
Person p = new Person();
p.Name = txtname.Text;
p.Family = txtfamily.Text;
p.Telephone = txttell.Text;
p.Major = txtmajor.Text;
DB.Insert(p);
txttell.Text = "";
txtmajor.Text = "";
txtname.Text = "";
txtfamily.Text = "";
List<Person> people = DB.GetPeople();
dataGridView1.DataSource = people;

Choose your ACCDB file listed in your project files, select Copy To Output Directory and set its value to Never (And remember that |DataDirectory| is a substitution strings that points (for ASP.NET projects) to APP_DATA, your record is inserted in the database copied in that directory.
Said that please consider to use a parameterized query to create an sql command, not string concatenations
try
{
OleDbCommand cmd = con.CreateCommand();
con.Open();
string s = "INSERT INTO Industrialist (S_Name,S_Family,S_Telephone,S_Major)VALUES(" +
"?,?,?,?)";
cmd.CommandText = s;
cmd.Parameters.AddWithValue("#p1",p.Name);
cmd.Parameters.AddWithValue("#p2",p.Family);
cmd.Parameters.AddWithValue("#p3",p.Telephone);
cmd.Parameters.AddWithValue("#p4",p.Major);
cmd.ExecuteNonQuery();
con.Close();
System.Windows.Forms.MessageBox.Show("Record successfully Added");
}
catch (OleDbException exp) { MessageBox.Show(exp.ToString()); }
Of course do not close the connection before executing the command.
Another point to change is the usage pattern of your connection. Do not create a global connection and keep it around for the lifetime of your application. Simply create and use it when needed and close/dispose immediately after
using(OleDbConnection con = new OleDbConnection("Provider=MICROSOFT.ACE.OLEDB.12.0; " +
"Data Source=|DataDirectory|//Phonebook-db.accdb;" +
"Persist Security Info=True"))
{
try
{
OleDbCommand cmd = con.CreateCommand();
....
}
} // <- Here at the closing brace the connectio will be close and disposed

Data addition and updation in SQL tables

Iam fairly new to SQLClient and all, and iam having a problem with my SQL tables..when ever i run my code, the data, rather than getting updated, attaches itself to the already existing records in the tables..here's my code
SqlConnection conneciones = new SqlConnection(connectionString);
SqlCommand cmd;
conneciones.Open();
//put values into SQL DATABASE Table 1
for (int ok = 0; ok < CleanedURLlist.Length; ok++)
{
cmd = new SqlCommand("insert into URL_Entries values('" + CleanedURLlist[ok] + "' , '" + DateTime.Now + "' , '" + leak + "' )", conneciones);
cmd.ExecuteNonQuery();
}
conneciones.Dispose();

Take a look at these functions, i hope you understand better on update , insert and delete functions..
Code snippets for reading, inserting, updating and deleting a records using asp.net and c# and sql server database
static void Read()
{
try
{
string connectionString =
"server=.;" +
"initial catalog=employee;" +
"user id=sa;" +
"password=sa123";
using (SqlConnection conn =new SqlConnection(connectionString))
{
conn.Open();
using (SqlCommand cmd = new SqlCommand("SELECT * FROM EmployeeDetails", conn))
{
SqlDataReader reader = cmd.ExecuteReader();
if (reader.HasRows)
{
while (reader.Read())
{
Console.WriteLine("Id = ", reader["Id"]);
Console.WriteLine("Name = ", reader["Name"]);
Console.WriteLine("Address = ", reader["Address"]);
}
}
reader.Close();
}
}
}
catch (SqlException ex)
{
//Log exception
//Display Error message
}
}
static void Insert()
{
try
{
string connectionString =
"server=.;" +
"initial catalog=employee;" +
"user id=sa;" +
"password=sa123";
using (SqlConnection conn =new SqlConnection(connectionString))
{
conn.Open();
using (SqlCommand cmd = new SqlCommand("INSERT INTO EmployeeDetails VALUES(" +
"#Id, #Name, #Address)", conn))
{
cmd.Parameters.AddWithValue("#Id", 1);
cmd.Parameters.AddWithValue("#Name", "Amal Hashim");
cmd.Parameters.AddWithValue("#Address", "Bangalore");
int rows = cmd.ExecuteNonQuery();
//rows number of record got inserted
}
}
}
catch (SqlException ex)
{
//Log exception
//Display Error message
}
}
static void Update()
{
try
{
string connectionString =
"server=.;" +
"initial catalog=employee;" +
"user id=sa;" +
"password=sa123";
using (SqlConnection conn = ew SqlConnection(connectionString))
{
conn.Open();
using (SqlCommand cmd =
new SqlCommand("UPDATE EmployeeDetails SET Name=#NewName, Address=#NewAddress WHERE Id=#Id", conn))
{
cmd.Parameters.AddWithValue("#Id", 1);
cmd.Parameters.AddWithValue("#Name", "Munna Hussain");
cmd.Parameters.AddWithValue("#Address", "Kerala");
int rows = cmd.ExecuteNonQuery();
//rows number of record got updated
}
}
}
catch (SqlException ex)
{
//Log exception
//Display Error message
}
}
static void Delete()
{
try
{
string connectionString =
"server=.;" +
"initial catalog=employee;" +
"user id=sa;" +
"password=sa123";
using (SqlConnection conn = ew SqlConnection(connectionString))
{
conn.Open();
using (SqlCommand cmd =
new SqlCommand("DELETE FROM EmployeeDetails " +
"WHERE Id=#Id", conn))
{
cmd.Parameters.AddWithValue("#Id", 1);
int rows = cmd.ExecuteNonQuery();
//rows number of record got deleted
}
}
}
catch (SqlException ex)
{
//Log exception
//Display Error message
}
}

Your code should be inserting new records, but I'm not clear on whether it is not doing that, or you mean to update existing records.
Aside from that, understanding that you are new to working with SQL Server, there are a couple of things you should be aware of.
You should use using to automatically dispose resources. This will also close your connection for you so you don't have open connections hanging around.
You should use parameters to protect against sql injection attacks. Another benefit of using parameters in your case is that you don't need to create new commands for every statement.
For example:
using (var connection = new SqlConnection(connectionString)
using (var command = connection.CreateCommand())
{
command.CommandText = "insert into URL_Entries values(#url, #now, #leak)";
command.Parameters.AddWithValue("#now", DateTime.Now);
command.Parameters.AddWithValue("#lead", leak);
// update to correspond to your definition of the table column
var urlParameter = command.Parameters.Add(new SqlParameter("#url", SqlDbType.VarChar, 100));
connection.Open();
for (int ok = 0; ok < CleanedURLlist.Length; ok++)
{
urlParameter.Value = CleanedURLlist[ok];
command.ExecuteNonQuery();
}
}
Per your comment, if you want to do an update, you'll need to include the parameter(s) that identify the rows to update. If this is a single row, use the primary key value:
command.CommandText = "update URL_Entries set UrlColumn = #url, ModifiedDate = #now where ID = #id";

You're using an INSERT function, that is 'ADD NEW RECORDS'
If you want an update, you'll want an UPDATE function
UPDATE tablename
SET column1 = 'x', column2 = 'y'
WHERE id = z

Creating a database using Connector/NET Programming?

How to create a database using connector/net programming? How come the following doesn't work?
string connStr = "server=localhost;user=root;port=3306;password=mysql;";
MySqlConnection conn = new MySqlConnection(connStr);
MySqlCommand cmd;
string s0;
try
{
conn.Open();
s0 = "CREATE DATABASE IF NOT EXISTS `hello`;";
cmd = new MySqlCommand(s0, conn);
conn.Close();
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}

You need to execute the command and also make sure to properly dispose objects:
string connStr = "server=localhost;user=root;port=3306;password=mysql;";
using (var conn = new MySqlConnection(connStr))
using (var cmd = conn.CreateCommand())
{
conn.Open();
cmd.CommandText = "CREATE DATABASE IF NOT EXISTS `hello`;";
cmd.ExecuteNonQuery();
}

You might want to execute the MySqlCommand. Now you just create one, but it doesn't execute your query.
Try this:
conn.Open();
s0 = "CREATE DATABASE IF NOT EXISTS `hello`;";
cmd = new MySqlCommand(s0, conn);
cmd.ExecuteNonQuery();
conn.Close();

execute your command and try this function
public void createDatabase(string server, string port, string database, string username, string password)
{
string connectionstring = string.Format("Server = {0}; Port ={1}; Uid = {2}; Pwd = {3}; pooling = true; Allow Zero Datetime = False; Min Pool Size = 0; Max Pool Size = 200; ", server, port, username, password);
using (var con = new MySqlConnection { ConnectionString = connectionstring })
{
using (var command = new MySqlCommand { Connection = con })
{
if (con.State == ConnectionState.Open)
con.Close();
try
{
con.Open();
}
catch (MySqlException ex)
{
msgErr(ex.Message + " connection error.");
return;
}
try
{
command.CommandText = #"CREATE DATABASE IF NOT EXISTS #database";
command.Parameters.AddWithValue("#database", database);
command.ExecuteNonQuery();//Execute your command
}
catch (MySqlException ex)
{
msgErr(ex.Message + " sql query error.");
return;
}
}
}
}

Imports MySql.Data.MySqlClient
Public Class Form1
Private dBf As String = "Empresa"
Private str As String = "Server = localhost; uid=root; pwd=;Database=mysql; pooling=false;"
Private Cmd As MySqlCommand
Private Con As New MySqlConnection(str)
Private Sub Form1_Load() Handles MyBase.Load
Try
Con.Open()
Cmd = New MySqlCommand("Create Database If Not exists " + dBf, Con)
Cmd.ExecuteNonQuery() : Con.ChangeDatabase(dBf)
Cmd = Con.CreateCommand
Cmd.CommandText = "CREATE TABLE Empleado" &
"(Id Char(10) COLLATE utf8_spanish_ci Not Null," &
"name VarChar(50) COLLATE utf8_spanish_ci Not Null," &
"email VarChar(50) COLLATE utf8_spanish_ci Not Null," &
"website VarChar(50) COLLATE utf8_spanish_ci Not Null," &
"Primary Key(id)) ENGINE=MyISAM"
Cmd.ExecuteNonQuery()
MsgBox("Registros, ok!!!") : Con.Close()
Catch ex As Exception
MsgBox(Err.Description)
End Try
End Sub
End Class