c# - Cannot add object to context.DbSet. SaveChanges not working -


i have method in controller:

public actionresult reserve(int id) {     viewbag.staffid = new selectlist(context.staffs, "staffid", "fname");     viewbag.roomid = id;     return view(); }

the corresponding view:

@model _00002165.models.reservation  @{     viewbag.title = "reserve"; }  <h2>reserve</h2>  @using (html.beginform()) {     @html.validationsummary(true)       <div class="editor-label">         <label>room number</label>     </div>     <div class="editor-field">         <input type="text" value="@viewbag.roomid" readonly name="roomid"/>     </div>      <div class="editor-label">         @html.labelfor(model => model.fromdate)     </div>     <div class="editor-field">         @html.textboxfor(model => model.fromdate)         @html.validationmessagefor(model => model.fromdate)     </div>     <div class="editor-label">         @html.labelfor(model => model.todate)     </div>     <div class="editor-field">         @html.textboxfor(model => model.todate)         @html.validationmessagefor(model => model.todate)     </div>      <div class="editor-label">         <label>staff:</label>     </div>     <div class="editor-field">         @html.dropdownlist("staffid", "select staff")         @html.validationmessagefor(model => model.staffid)     </div>     <button type="submit">reserve</button> }

and want save data these inputs these post method:

[httppost] public actionresult reserve(reservation res) {     if (modelstate.isvalid)     {         var customer = context.customers.first(x => x.username == user.identity.name);         res.customerid = customer.customerid;         context.reservation.add(res);         context.entry(res).state = entitystate.modified;         context.savechanges();         return redirecttoaction("index");     } }

this giving me following error:

store update, insert, or delete statement affected unexpected number of rows (0).

people suggest add @html.hiddenfor(model => model.reservationid) view.

but model.reservationid empty.

how can fix this? please help

you shouldn't passing data transfer objects to/from views. create view model tomodel method return dto want. adding context, don't need change state.

use this

context.reservation.add(res); context.savechanges();

removing

context.entry(res).state = entitystate.modified;

if trying update, pull record database, make changes , call savechanges


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