Dear sir,

As per your direction i wrote the code.

Restore database Error: The file cannot be overwritten. It is being used by another database

But still it is error

Incorrect syntax near 'VMS'.

Incorrect syntax near the keyword 'with'. If this statement is a common table expression, an xmlnamespaces clause or a change tracking context clause, the previous statement must be terminated with a semicolon.

        private void button2_Click(object sender, EventArgs e)
        {
            //con1 = new SqlConnection("Data Source=" + comboBox1.Text + ";Database=Master;data source=.; Initial Catalog=" + comboBox2.Text + "; uid=sa; pwd=321;");
            SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["VMS"].ToString());
            string database = con.Database.ToString();
            
                if(con.State!=ConnectionState.Open)
                {
                    con.Open();                    
                }
                try
                {                    
                    string sqlStmt2 = string.Format("ALTER DATABASE[" + database + "]SET SINGLE_USER WITH ROLLBACK AFTER 5");

                    SqlCommand cmd = new SqlCommand(sqlStmt2, con);
                    cmd.ExecuteNonQuery();

                    string sqlstmt3 = "USE MASTER RESTORE DATABASE[" + database + "] FROM DISK='" + textBox1.Text + "';WITH MOVE'" + cmblogicalnamemdf.Text + "'TO'" + textBox2.Text + "',MOVE'" + cmdlogicalnameldf.Text + "'TO'" + textBox3.Text + "' WITH REPLACE MOVE;";
                    SqlCommand cmd1 = new SqlCommand(sqlstmt3, con);
                    cmd1.ExecuteNonQuery();

                    string sqlstmt4 = string.Format("ALTER DATABASE[" + database + "]SET MULTI_USER");
                    SqlCommand cmd2 = new SqlCommand(sqlstmt4, con);
                    cmd2.ExecuteNonQuery();

                    MessageBox.Show("database restoration done successfully");
                    con.Close();
                }
                catch(Exception ex)
                {
                    MessageBox.Show(ex.ToString());
                }
         }