c# - How to pass back list of items as model from view to controller? -

i have model (see below) , user should able @ single spend details (already working ajax , dropdown driven). once spend details loaded should able enter in either total amount details, or break down category (which coming different model (spendcategories) prepopulated). first iterate through categories pull them , each row map spendcategoryname spendcategory in spendbreakdown.cs. trying iterate , generate textarea per spendcategory name , send whole model (budgets).

problem

when run gives me argument out of range exeception on hiddenfor line in loop. need way save amounts , categories on post back. unfortunately new mvc , cannot change way model set up. working except piece.

i had scrub of down privacy purposes please let me know if need clarification

model

public class budgets : financials {     public spend spending { get; set; }     public spenddetails spendingdetails { get; set; }     public list<spendbreakdown> spendingbreakdown{ get; set; } } 

spend.cs

public int spendid {get; set;} public list<spendcategories> spendcategories {get; set;} 

spendcategories.cs (pre populated data)

public int spendcategoryid {get; set;} public string spendcategoryname {get; set;} public string spendcategorydescription {get; set;} 

spenddetails.cs

public int spenddetailsid {get; set;} public int spendid {get; set;} public string spenddetailname {get; set;} public int spendbreakdownid {get; set;} public decimal totalspendamount {get; set;} 

spendbreakdown.cs

public int spendbreakdownid {get; set;} public int spenddetailsid {get; set;} public decimal spendbreakdownamount {get; set;} public string spendcategory {get; set;} 

partial view on main page calling partial has submit form

    <div class="row col-md-5">     <div class="table-responsive">         <table class="table-bordered">             <thead>                 <tr>                     <th class="dt-head-center">category:</th>                     <th>total amount: </th>                 </tr>             </thead>             <tbody>                 <tr>                     <td>@html.displayfor(model => model.spenddetails.spendcategories)</td>                     <td>@html.textareafor(model => model.spenddetails.totalspendamount)</td>                 </tr>             </tbody>         </table>     </div> </div> <div class="row totals">     <div class="table-responsive col-md-6">         <table class="table table-bordered table-condensed table-responsive" id="tblspendsummary" summary="spend summary" style="padding-left: 10px;">             <thead>                 <tr class="summary-header">                     <th class="dt-head-center">spend category name</th>                     <th class="dt-head-center">spend breakdown amount</th>                 </tr>             </thead>             <tbody>                  @foreach (var cat in model.spend.spendcategories)                 {                     <tr>                         <td>@cat.spendcategoryname- @cat.spendcategorydescription</td>                          @for (int = 0; < model.spend.spendcategories.count(); i++)                         {                             @html.hiddenfor(model => model.spendbreakdown[i].spendcategory, new { @value = @cat.spendcategorydescription })                             @*@html.hiddenfor(model => model.spendbreakdown[i].spendbreakdownid)*@                             <td>@html.textareafor(model => model.spendbreakdown[i].spendbreakdownamount)</td>                         }                     </tr>                 }             </tbody>         </table>     </div> </div> 

ui

controller (called populate model on dropdownlist change

public actionresult budgettotalamount(int spenddetailsid)     {         var spendid = _executionrepository.retrievespendidbyspenddetailsid (spenddetailsid).spendid;          var model = new budgets         {             spending = _executionrepository.retrievespendidbyspenddetailsid(spenddetailsid),             spendingdetails = _executionrepository.retrievespendspenddetailsbyspenddetailsid(spenddetailsid),             spendingbreakdown = _executionrepository.retrievespendbreakdown(spendid, spenddetailsid)         };          return partialview("budgets/_spendbudgetstotalamounts", model);     } 

you using count of spendcategories index:

@for (int = 0; < model.spend.spendcategories.count(); i++) 

but indexing spendbreakdown:

@html.hiddenfor(model => model.spendbreakdown[i].spendcategory, new { @value = @cat.spendcategorydescription }) 

these 2 items not have same number of items, index going beyond end of spendbreakdown. make sure populated correctly if supposed correlate. otherwise, use foreach on spendbreakdowns.