private string GetConnectionString()
        {
            if (File.Exists(Application.StartupPath + "\\Process.config") && ConnectionString == "")
            {
                XmlDocument xml = new XmlDocument();
                xml.Load(Application.StartupPath + "\\Process.config");
                XmlNode comment = xml.SelectSingleNode("Config");
                ConnectionString = comment.ChildNodes[0].InnerText;
            }
            return ConnectionString;
        }

        private void SQLQuery_exec(string SQL)
        {
            try
            {
                SqlConnection selectConnection1 = new SqlConnection(GetConnectionString());
                SqlCommand comm = new SqlCommand(SQL, selectConnection1);
                selectConnection1.Open();
                comm.CommandTimeout = 0;
                comm.ExecuteNonQuery();
                selectConnection1.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "Ошибка выполнения запорса", MessageBoxButtons.OK, MessageBoxIcon.Error, MessageBoxDefaultButton.Button1);
                clear_all();
            }
        }

        private DataTable SQLQuery(string SQL)
        {
            try
            {
                SqlConnection selectConnection2 = new SqlConnection(GetConnectionString());
                SqlDataAdapter adapter = new SqlDataAdapter(SQL, selectConnection2);
                DataSet ds = new DataSet();
                selectConnection2.Open();
                adapter.SelectCommand.CommandTimeout = 0;
                adapter.Fill(ds);
                selectConnection2.Close();
                return ds.Tables[0];
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "Ошибка запорса", MessageBoxButtons.OK, MessageBoxIcon.Error, MessageBoxDefaultButton.Button1);
                clear_all();
                return null;
            }
        }

Data Source=10.1.0.6;Initial Catalog=Log;Persist Security Info=True;User ID=a;Password=123

selectConnection1.Open()