namespace ConnectionStringTesting
{
    public partial class Form1 : Form
    {
        SPSite _site; 
        public Form1()
        {
            InitializeComponent();
            CreateContext();
        }
        private void CreateContext()
        {
            _site = new SPSite("http://adfsaccount:2222/"); 
        }
        private void btnAdmin_Click(object sender, EventArgs e)
        {
            Config config = (Config)_site.WebApplication.GetChild<Config>("a5");
            if (config == null)
            {
                txtConnectionString.Text = " Connection String is not set yet ";
            }
            else
            {
                txtConnectionString.Text = config.ConnectionString;
            }
            pnlAdmin.Visible = true;
        }
        private void btnOk_Click(object sender, EventArgs e)
        {
            Config config = (Config)_site.WebApplication.GetChild<Config>(" connectionstring ");
            if (config == null)
            {
                config = new Config("connectionstring ", _site.WebApplication);
                if (!string.IsNullOrEmpty(txtConnectionString.Text))
                {
                    config.ConnectionString = txtConnectionString.Text;
                }
                else
                {
                    config.ConnectionString = "Connection String Not set ";
                }
                config.Update();
                MessageBox.Show("Connection String Got added "); 
            }
            else
            {
                config.ConnectionString = txtConnectionString.Text.ToString();
                config.Update();
                MessageBox.Show("Connection String Got Updated");
            }
            pnlAdmin.Visible = false; 
        }
        private void btnOperation_Click(object sender, EventArgs e)
        {
            Config config = (Config)_site.WebApplication.GetChild<Config>("connectionstring");
            if (config == null)
            {
                MessageBox.Show("Connection String is Not set ");
            }
            else
            {
                txtConnectionString.Text = config.ConnectionString;
                SqlConnection con = new SqlConnection(txtConnectionString.Text);
                try
                {
                    con.Open();
                    DataTable dt = new DataTable();
                    string strQuery = "select * from Person.Address";
                    SqlCommand cmd = new SqlCommand(strQuery, con);
                    cmd.CommandType = CommandType.Text;
                    SqlDataAdapter ada = new SqlDataAdapter();
                    ada.SelectCommand = cmd;
                    ada.Fill(dt);
                    dataGridView1.DataSource = dt;
                    pnlOperation.Visible = true;
                }
                catch (Exception ex)
                {
                    MessageBox.Show("Connection String is not Correct!!! Go to Admin link and make it correct ");
                }
            }
        }
        private void btnOperationOK_Click(object sender, EventArgs e)
        {
            pnlOperation.Visible = false; 
        }
    }
}
Conclusion
In this article, we saw How to configure connection string using SPPersistedObject. Thanks for reading.