How we can take back up of SQL from C#

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C#

i have a form and there is two Button in my form one for Select Folder and 2nd for take back up of database which is currently used for my project i want to take backup of my database on backup button click.
and also take Restore database using C#
Any One Help me.
I'm trying this code button i am facing error.
Thanks in Advance.

error is
system.sql.sqlclint.sqlexception:Cannot open Backup device.
operating system error. access denied.
Backup database terminating abnormally

What I have tried:

using (SqlConnection conn4 = new SqlConnection(DbConfigClass.connectDb()))
            {
                string database = conn4.Database.ToString();
                try
                {
                    if (PathtextBox.Text == string.Empty)
                    {

                    }
                    else
                    {                       
                        string cmd = "BACKUP DATABASE ["+database+"] TO DISK '"+PathtextBox.Text+"\\"+"Database"+"-"+DateTime.Now.Ticks.ToString("yyyy-MM-dd--HH-mm-ss")+ ".back'";
                        using (SqlCommand comand = new SqlCommand(cmd, conn4))
                        {
                            if (conn4.State != ConnectionState.Open)
                            {
                                conn4.Open();
                            }
                            comand.ExecuteNonQuery();
                            conn4.Close();
                            MessageBoxClass.ShowSucessMessage("Successful to backup data","Successful");
                        }
                    }
                }
                catch (Exception es)
                {
                    MessageBoxClass.ShowErrorMessage("" + es, "");
                }
            }