c# - Cannot Save Data in my database using a DataGridView -

i have made application can add,view,update , delete data database using datagridview. have made separate forms each operation using dgv. in update form i'm not able update or edit data dgv , data not stored in database dgv. please tell me correct code. code

    public update()     {         initializecomponent();     }      sqlconnection sql_con;     sqlcommand sql_cmd;     sqldataadapter sql_ad;     sqlcommandbuilder sql_cb;     datatable dt;     dataset ds;     string connect_string;      private void update_load(object sender, eventargs e)     {         datagridview1.refresh();          connect_string = @"data source=.\sqlexpress;attachdbfilename=c:\users\administrator\desktop\form\form\employeedb.mdf;integrated security=true;user instance=true";             // todo: line of code loads data 'ds_employeedb.emp_info' table. can move, or remove it, needed.         this.emp_infotableadapter.fill(this.ds_employeedb.emp_info);           string select_cmd = "select * emp_info";         sql_con = new sqlconnection(connect_string);         sql_con.open();         sql_cmd = new sqlcommand(select_cmd,sql_con);         sql_ad = new sqldataadapter(sql_cmd);         sql_cb = new sqlcommandbuilder(sql_ad);         ds = new dataset();         sql_ad.fill(ds,"emp_info");         dt=ds.tables["emp_info"];         sql_con.close();         datagridview1.datasource = dt;      }      private void button_search_click(object sender, eventargs e)     {         string select_cmd = "select * emp_info f_name='" + textbox_search.text + "'";          sql_con = new sqlconnection(connect_string);         dt = new datatable();         sql_ad = new sqldataadapter(select_cmd, sql_con);         sql_ad.fill(dt);         datagridview1.datasource = dt;     }        private void datagridview1_cellendedit(object sender, datagridviewcelleventargs e)     {         datagridview1.refresh();     }      private void button_update_click(object sender, eventargs e)     {          string update_query = "update emp_info set " +             "f_name = '" + datagridview1.selectedrows[0].cells[1].value.tostring() + "' ," +             "l_name = '" + datagridview1.selectedrows[0].cells[2].value.tostring() + "' ," +             "father_name = '" + datagridview1.selectedrows[0].cells[3].value.tostring() + "' ," +             "education = '" + datagridview1.selectedrows[0].cells[4].value.tostring() + "' ," +             "institute = '" + datagridview1.selectedrows[0].cells[5].value.tostring() + "' ," +             "address = '" + datagridview1.selectedrows[0].cells[6].value.tostring() + "' ," +             "phone = '" + datagridview1.selectedrows[0].cells[7].value.tostring() + "' ," +             "cinc = '" + datagridview1.selectedrows[0].cells[8].value.tostring() + "' ," +             "where '" + textbox_search.text + "'";          sql_con = new sqlconnection(connect_string);         sql_con.open();         sql_cmd = new sqlcommand(update_query, sql_con);         sql_ad = new sqldataadapter(sql_cmd);         sql_cb = new sqlcommandbuilder(sql_ad);         ds = new dataset();         sql_ad.fill(ds, "emp_info");         dt = ds.tables["emp_info"];         sql_con.close();         datagridview1.datasource = dt;     }      private void button_cancle_click(object sender, eventargs e)     {         close();     } } 

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