the connection string property has not been initalize

Question

private void btn_browse_Click(object sender, EventArgs e)

{

FolderBrowserDialog dl = new FolderBrowserDialog();

if (dl.ShowDialog() == DialogResult.OK)

{

tbx_bacup.Text = dl.SelectedPath;

btn_buckup.Enabled = true;

}

}

private void btn_buckup_Click(object sender, EventArgs e)

{

string database = con.Database.ToString();

try

{

if (tbx_bacup.Text == string.Empty)

{

MessageBox.Show("please inter backup file location");

}

else

{

string cmd = "BACKUP DATABASE [" + database + "] TO DISK ='" + tbx_bacup.Text + "\\" + " DATABASE " + "-" + DateTime.Now.ToString("yyyy-MM-dd--HH-mm-ss") + ".back'";

using (SqlCommand command = new SqlCommand())

{

if (con.State != ConnectionState.Open)

{

con.Open();

}

command.ExecuteNonQuery();

con.Close();

MessageBox.Show("Database backup succefily ");

btn_buckup.Enabled = true;

}

}

}

catch (Exception ex)

{

MessageBox.Show(ex.Message);

}

}

private void btn_restoreee_Click(object sender, EventArgs e)

{

OpenFileDialog pn = new OpenFileDialog();

pn.Filter = "SQL SERVER database backup files |*.bak";

pn.Title = " Database restore ";

if (pn.ShowDialog() == DialogResult.OK)

{

tbx_restore.Text = pn.FileName;

btn_restore.Enabled = true;

}

}

private void btn_restore_Click(object sender, EventArgs e)

{

string database = con.Database.ToString();

try

{

if (con.State != ConnectionState.Open)

{

con.Open();

}

string sql = string.Format("ALTER DATABASE[" + database + "] SET SINGLE_USER WITH ROOLLBACK IMMEDIATE");

SqlCommand cmd = new SqlCommand(sql, con);

cmd.ExecuteNonQuery();

string sqll = string.Format("USE MASTER RESTORE DATABASE [" + database + "] FROM DISK ='" + tbx_restore.Text + "' WITH REPLACE;");

SqlCommand cmdd = new SqlCommand(sqll, con);

cmd.ExecuteNonQuery();

string sqlll = string.Format("ALTER DATABASE [" + database + "] SET MULTI_USER");

SqlCommand cmddd = new SqlCommand(sqlll, con);

cmd.ExecuteNonQuery();

MessageBox.Show("database restoration succefily");

con.Close();

}

catch (Exception ex)

{

MessageBox.Show(ex.ToString());

}

}