MVC error... please help how to fix it

The Error Message Is-

(The ViewData item that has the key 'DistrictId' is of type 'System.Int32' but must be of type 'IEnumerable')

// My Controller is-

//The problem is related to DistrictId

[HttpPost]

[ValidateAntiForgeryToken]

//STORING THE DATA into the database

public ActionResult Insert(ObjectModel OM, HttpPostedFileBase Photo, HttpPostedFileBase Resume, HttpPostedFileBase IdProof)

{

if (ModelState.IsValid) //checking model is valid or not

{

DB objDB = new DB(); //calling class DBdata

// i am showing only DistrictId and related details , I deleted rest of the code which is not useful for here ...

int DistrictIdInt = Convert.ToInt32(OM.DistrictId);

OM.DistrictId = DistrictIdInt;

int result = objDB.InsertEmployementApplication(OM); // passing Value to DBClass from model

//I think the problem is occured after THIS SECTION

ModelState.Clear(); //clearing model

return View(OM);

}

}

else

{

var errors = ModelState.Values.SelectMany(v => v.Errors);

ModelState.AddModelError("", "Error in saving data");

return View();

}

// My Model is-

// The Data is getting saved in my database but this error is popping up again and again.

{

//iT ASKS for districtId to be 'IEnumerable' rather than Int....I dont get it why...its the list which is IEnumerable not DistrictId

[Display(Name = "Select District")]

public IList DistrictNamesModel { get; set; }

[Required(ErrorMessage = "Please Select District")]

public int DistrictId { get; set; }

}

//My View is-

//the problem is in dropDownlistFor Tag..

@model MVCtrendsetters.Models.ObjectModel

@{

ViewBag.Title = "Insert";

}

Insert

@using (Html.BeginForm("Insert", "AppForm", FormMethod.Post,

new { @enctype = "multipart/form-data" }))

{

@Html.AntiForgeryToken()

@Html.ValidationSummary(true)

ObjectModel

@Html.DropDownListFor(x => x.DistrictId, Model.DistrictNamesModel , "--Select--", new { @id = "ddlDistrict"});

}