How to update data in mvc3 using stored procedure

See more:

C#

SQL-Server

MVC3

I am new in mvc3 i have added my code please resolve this
I am getting this error while click on button in edit form
"Unable to cast object of type 'System.Int32' to type 'System.String'."

my db is

CharityID int
City varchar(20)

ALTER PROCEDURE [dbo].[Usp_Charities_Federations_Update]  
(    
@CharityID int,

 @City        varchar(50)    

)        
      
AS        
Begin  
  Update Charity set

 City=  @City

End    

execute Usp_Charities_Federations_Update 50,'Gajuwak'

This is Controller:

#region AcctionLink for EditCharity START
        [HttpGet]
        public ActionResult AddCharity(int charityID=0)
        {
            CharityModel objCharityModel = new CharityModel();
            objCharityModel = GetCharityRecord(charityID);
            
            return View(objCharityModel);
        }

        [HttpPost]
        public ActionResult AddCharity(CharityModel objCharityModel)
        {
            if (!ModelState.IsValid)
            {
                UpdateCharity(objCharityModel);
            }
            return View(objCharityModel);
        }
        public CharityModel GetCharityRecord(int cahrityID)
        {
            CharityModel objCharityModel = new CharityModel();
            var charityDetail = objEntities.Charities.Where(m => m.CharityID == cahrityID);
            if (charityDetail != null)
            {
                foreach (var item in charityDetail)
                {
                    objCharityModel.PCharityId = item.CharityID;
                   
                  
                    objCharityModel.PCity=item.City;
                 
                
                }
            }
            return objCharityModel;
        }

        public void UpdateCharity(CharityModel objCharityModel)
        {
            try
            {
                //Call your update function to update record
                objEntities.Update(
                    objCharityModel.PCharityId,
                  
                    objCharityModel.PCity ="Gajuwaka"
                   
                   
                    );
                ViewData["updatestatus"] = "1";
            }
            catch
            {
                ViewData["updatestatus"] = "0";
            }
        }
        #endregion

This is Model:

public class CharityModel
   {

     
      
       public int PCharityId { get; set; }
     
      
       public string PCity{ get; set; }

This is View:

@model PledgeNetApplication.Models.CharityModel
  <tr>
                                <td>
                                    CharityID:
                                </td>
                                <td style="width: 412px;">
                                    <div>
                                        @Html.TextBoxFor(m => m.PCharityId)
                                        
                                        <div class="inlineMessage">
                                        </div>
                                        <div style="clear: both">
                                        </div>
                                    </div>
                                </td>
                            </tr>
                            <tr>
                                <td>
                                    Charity Number:
                                </td>
                                <td style="width: 412px;">
                                    @Html.TextBoxFor(m => m.PCity) @Html.ValidationMessageFor(model => model.PCharityName)
                                </td>
                                <td id="PCharityName">
                                </td>
                            </tr>
<save button="">

while execute this data will be binded but when i update this error will appear.

"Unable to cast object of type 'System.Int32' to type 'System.String'."

My sp is executed successufully but from front the data will not be updated

so please help me.