I am getting an error in dropdown list. 

Overload resolution failed because no Public 'BindTo' is most specific for these arguments:
    'Public Function BindTo(dataSource As System.Collections.Generic.IEnumerable(Of SelectListItem)) As Kendo.Mvc.UI.Fluent.DropDownListBuilder':
        Not most specific.
    'Public Function BindTo(dataSource As System.Collections.Generic.IEnumerable(Of DropDownListItem)) As Kendo.Mvc.UI.Fluent.DropDownListBuilder':
        Not most specific.

This is the line where this exception is being thrown at:

    <div class="editor-field">
        @(Html.Kendo().DropDownList().Name("ExternalMailItemID").BindTo(ViewData("ExternalMailItem")))       
        @Html.ValidationMessageFor(Function(model) model.ExternalMailItemID)
        </div>

This is what i am doing in the controller:

   <HttpPost()> _
        Function Create(ByVal collection As ExternalMailCost) As ActionResult
            Try
                If _repositoryForMailItem.IsExternalMailItemExist(collection.ExternalMailItemID, collection.StartDate, collection.EndDate) = True Then
                    ModelState.AddModelError("", "Unable to add record. There is an overlapping record for this mail item")
                End If


                If ModelState.IsValid Then

                    'Check whether a cost has already been associated with the same mail item
                    ' if there is already cost associated, then check whether the dates selected overlapse?

                    _repositoryForMailCost.Save(collection, "VivekBa")
                End If
                Return View()

            Catch
                Return View()
            End Try
        End Function

The error is thrown when i add the error in the addmodelerror, otherwise it works fine. please help