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Connection must be valid and Open c# Winform

I am getting error:
Connection must be valid and Open c# Winform.
Here is my code, can anyone please help what is wrong in the below code?
public void NameSearch()
{
listBox1.Visible = true;
try
{
String constring = "datasource=localhost;port=3306;Initial Catalog = 'svms'; username = svms; password =svms2016CPU";
string query = "select * from studentinformation where StudLname='" + metroTextBox1.Text + "'";
MySqlConnection conDataBase = new MySqlConnection(constring);
MySqlCommand cmdDataBase = new MySqlCommand(query, conDataBase);
MySqlDataReader myReader = cmdDataBase.ExecuteReader();
while (myReader.Read())
{
string Lname = myReader.GetString(myReader.GetOrdinal("StudLname"));
string Fname = myReader.GetString(myReader.GetOrdinal("StudFname"));
string Mname = myReader.GetString(myReader.GetOrdinal("StudMname"));
string nameResult = Lname + ", " + Fname + " " + Mname;
listBox1.Items.Add(nameResult);
}
conDataBase.Close();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}

You haven't open connection before use it, Open connection
conDataBase.Open();

Open the conn before read:
conDataBase.Open();
Like:
String constring = "datasource=localhost;port=3306;Initial Catalog = 'svms'; username = svms; password =svms2016CPU";
string query = "select * from studentinformation where StudLname='" + metroTextBox1.Text + "'";
MySqlConnection conDataBase = new MySqlConnection(constring);
MySqlCommand cmdDataBase = new MySqlCommand(query, conDataBase);
//
conDataBase.Open();
//
MySqlDataReader myReader = cmdDataBase.ExecuteReader();

Can you help me to show datagridview and Refresh after update?

This is my code and error message when you running say:
An unhandled exception of type System.Data.SqlClient.SqlException
occurred in System.Data.dll
on this da.fill(dt);
SqlConnection con = new SqlConnection("Data Source=ANTONIANGGA-PC\\SQLEXPRESS;Initial Catalog=FullandStarving;Integrated Security=True");
SqlCommand cmd;
SqlDataAdapter da;
DataTable dt = new DataTable();
public FormProduksi()
{
InitializeComponent();
showgridview();
}
private void showgridview()
{
con.Open();
dt.Clear();
cmd = new SqlCommand("SELECT * FROM Produksi", con);
//cmd.CommandType = CommandType.StoredProcedure; done :D
da = new SqlDataAdapter(cmd);
da.Fill(dt);
dataGridView1.DataSource = dt;
con.Close();
}
private void button2_Click(object sender, EventArgs e)
{
//Datetimepicker to Database
string dProduksi = DateTime.Parse(dtmProduksi.Text).ToString("yyyy-MM-dd");
try{
con.Open();
cmd = new SqlCommand("insert into Produksi (IDProduksi,IDPhoto,TanggalProduksi,NamaKaryawan,KeteranganPhoto) Values('" + txtIdpro.Text + "','" + txtIdPhoto.Text + "','" + dProduksi + "','" + txtNamaKaryawan.Text + "','" + rxtKtrphoto.Text + "')", con);
cmd.ExecuteNonQuery();
MessageBox.Show("Update telah di jalankan");
showgridview();
clear();
con.Close();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
that update successfully but cant refresh, so i do quit that form and open can see it

You are closing the connection
con.Close();
and then using
da.Fill(dt);
Just swap this lines:
showgridview();
con.Close();
For example with DbDataAdapter.Fill:
Notes:
1
Yoy should use parametrized queries so you avoid SQL Injection attacks:
var cmd = new SqlCommand("SELECT EmpName FROM Employee WHERE EmpID = #id", con);
cmd.Parameters.AddWithValue("#id", id.Text);
2
Wrap SqlConnection and SqlCommand into using so any resources used by those would disposed:
string position;
using (SqlConnection con = new SqlConnection("server=free-pc\\FATMAH; Integrated Security=True; database=Workflow; "))
{
con.Open();
using (var cmd = new SqlCommand("SELECT EmpName FROM Employee WHERE EmpID = #id", con))
{
cmd.Parameters.AddWithValue("#id", id.Text);
var name = cmd.ExecuteScalar();
if (name != null)
{
position = name.ToString();
Response.Write("User Registration successful");
}
else
{
Console.WriteLine("No Employee found.");
}
}
}
Credit

Just change the showgridview() function as below where connection is opened & closed properly.
Also check your sql query ,provide space and maintain syntax of query :
SELECT * FROM Produksi
Error screenshot clearly depicts that stored procedure with such name don't exist
comment out those lines as code below :
void showgridview()
{
con.Open();
dt.Clear();
cmd = new SqlCommand("SELECT * FROM Produksi", con);
//cmd.CommandType = CommandType.StoredProcedure;
da = new SqlDataAdapter(cmd);
da.Fill(dt);
dataGridView1.DataSource = dt;
con.Close();
}
Then you wont be having connection issues and errors related .
Button Click code change the closing connection as below:
private void button2_Click(object sender, EventArgs e)
{
//Datetimepicker to Database
string dProduksi = DateTime.Parse(dtmProduksi.Text).ToString("yyyy-MM-dd");
try
{
con.Open();
cmd = new SqlCommand("insert into Produksi (IDProduksi,IDPhoto,TanggalProduksi,NamaKaryawan,KeteranganPhoto) Values('" + txtIdpro.Text + "','" + txtIdPhoto.Text + "','" + dProduksi + "','" + txtNamaKaryawan.Text + "','" + rxtKtrphoto.Text + "')", con);
cmd.ExecuteNonQuery();
MessageBox.Show("Update telah di jalankan");
con.Close();
showgridview();
clear();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
Also, for further reading:
parameterized queries vs. SQL injection
Why do we always prefer using parameters in SQL statements?

How to send the All items of combo Box To SQL DB using MySQL query

These are the values i want to send to the data base
private void radButton1_Click(object sender, EventArgs e)
{
string constring = "datasource=localhost;port=3306;username=root;";
string Query = "insert into rhms.reservation(no_table)values('" + this.comboBox1.SelectAll() + "');";
MySqlConnection condatabase = new MySqlConnection(constring);
MySqlCommand cmd = new MySqlCommand(Query, condatabase);
MySqlDataReader myread;
try
{
condatabase.Open();
myread = cmd.ExecuteReader();
MessageBox.Show("saved");
this.Refresh();
while (myread.Read())
{
}
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
}
}

You need set correct info at query string. Now it`s incorrect. Data must separated by commas:
string Query = "insert into rhms.reservation(no_table) values " + this.comboBox1.Items
.Select(p=>string.Format("({0})",p.ToString()))
.Aggregate((p1,p2)=>p1 + "," + p2) + ";"

Displaying values from a database on different rows in a textbox C#

I've been working on this program where it will pull accounts out of the database and will display them in a textbox I got this working so far but it will only pull the account from my database on the first row. Here is my code :
string myConnection = "datasource=xxxx;port=3306;username=xxxx;password=xxxx!";
string Query = "select * from xxx.xxx;";
MySqlConnection conDataBase = new MySqlConnection(myConnection);
MySqlCommand cmdDataBase = new MySqlCommand(Query, conDataBase);
MySqlDataReader myReader;
DataTable dt = new DataTable();
try
{
conDataBase.Open();
myReader = cmdDataBase.ExecuteReader();
while (myReader.Read())
{
string sUsername = myReader.GetString("usernames");
string sPasswords = myReader.GetString("passwords");
nsTextBox1.Text = sUsername + ":" + sPasswords;
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
Also is there anyway so it will erase the old Username + Password and show the new one that is pulled?

Like this?:
nsTextBox1.Text += sUsername + ":" + sPasswords + Enviroment.NewLine;
Also, your TextBox needs to be multiline.
Must it be a TextBox? Why not use a ListBox?

Windows Form Application update query not save data

I try to use an update query in my C# windows form application. I do not get any errors, it just seems not to save the data I try to update. Take a look at the code:
private void button2_Click(object sender, EventArgs e)
{
try
{
string myConnection = connection;
MySqlConnection myConn = new MySqlConnection(myConnection);
myConn.Open();
MySqlDataAdapter myDataAdapter = new MySqlDataAdapter();
myDataAdapter.UpdateCommand = new MySqlCommand(" update users set username=" + textBox1.Text + " where username=" + username + " ", myConn);
MySqlCommandBuilder cb = new MySqlCommandBuilder(myDataAdapter);
DataSet ds = new DataSet();
myConn.Close();
MessageBox.Show("Changes has been saved.");
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
}
The username is an string passed from another form (gridview) ..

I found an solution for this on the internet. What I cam up with is:
private void button2_Click(object sender, EventArgs e)
{
string myConnection = connection;
MySqlConnection myConn = new MySqlConnection(myConnection);
MySqlCommand cmdDataBase = new MySqlCommand("UPDATE `users` SET username='Test' WHERE username='CurrentName' ", myConn);
MySqlDataReader myReader;
try
{
myConn.Open();
myReader = cmdDataBase.ExecuteReader();
myConn.Close();
MessageBox.Show("Changes has been saved!");
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}