'An item with the same key has already been added' - html

Question

I am trying to send some data to the database via this form. I keep getting the error about an item with the same key has already been added.
I have been trying to debug this error for quite some time now. I did have several elements that were getting assigned the same name by their #Html helpers, but I thought I cleared them up.
<div id="addNewUser" class="newUser" style="border: solid black 2px">
<form name="newUser" method="post" action="#Url.Action("Submit", "Roles")">
<h4>Add New User</h4>
<div style="display: flex; justify-content: space-between">
<div id="ddlNewUserHealthPlan" class="form-group">
#Html.DropDownListFor(m => m.NewUserHealthPlans, (IEnumerable<SelectListItem>)Model.GetHealthPlans(Model.HEALTHPLAN), "Select a Healthplan", new { #class = "form-group", #id = "ddlNewUserHealthPlanSelect" })
</div>
<div id="ddlNewUserRoles" class="form-group">
#Html.DropDownListFor(m => m.Roles, (IEnumerable<SelectListItem>)Model.GetUserRoles(Model.USERROLE), "Select a Role", new { #class = "form-group", #id = "ddlNewUserRoleSelect" })
</div>
</div>
<div style="display: flex; justify-content: space-between">
<div class="form-group">
#Html.Label("User Id: ")
#Html.TextBoxFor(m => m.User_Id, new { #class = "form-control" })
</div>
<div id="ddlNewUserPrimaryHP" class="form-group">
#Html.DropDownListFor(m => m.NewUserPrimaryHealthPlan, (IEnumerable<SelectListItem>)Model.GetHealthPlans(Model.HEALTHPLAN), "Select a Primary Healthplan", new { #class = "form-group", #id = "newUserPrimaryHP" })
</div>
</div>
<br />
<div style="display: flex; justify-content:center">
<button type="submit" class="btn btn-primary">Add new User</button>
</div>
</form>
</div>
Saving the user
public void SaveUser(SearchRolesViewModel objSearchRolesViewModel, string userID)
{
USERACCOUNT objUserAccount = new USERACCOUNT
{
HPID = Convert.ToInt32(objSearchRolesViewModel.NewUserHealthPlans),
DOMAIN = "Aeth",
NTUSERID = objSearchRolesViewModel.User_Id,
ROLEID = Convert.ToInt32(objSearchRolesViewModel.UserRole),
FIRSTNAME = "Matthew",
LASTNAME = "Wright",
EMAIL = "MW#test.com",
ACTIVE = Convert.ToBoolean(objSearchRolesViewModel.ActiveStatus),
DEFAULTPLANID = Convert.ToInt32(objSearchRolesViewModel.NewUserPrimaryHealthPlan),
CREATEID = userID,
CREATEDATE = DateTime.Now,
UPDATEID = userID,
UPDATEDATE = DateTime.Now
};
_context.USERACCOUNTs.Add(objUserAccount);
_context.SaveChanges();
}
Stack Trace
[ArgumentException: An item with the same key has already been added.]
System.ThrowHelper.ThrowArgumentException(ExceptionResource resource) +52
System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add) [phone]
System.Collections.Generic.CollectionExtensions.ToDictionaryFast(TValue[] array, Func`2 keySelector, IEqualityComparer`1 comparer) +116
System.Web.Mvc.ModelBindingContext.get_PropertyMetadata() +149
System.Web.Mvc.DefaultModelBinder.BindProperty(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor) +176
System.Web.Mvc.DefaultModelBinder.BindProperties(ControllerContext controllerContext, ModelBindingContext bindingContext) +101
System.Web.Mvc.DefaultModelBinder.BindComplexElementalModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Object model) +55
System.Web.Mvc.DefaultModelBinder.BindComplexModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +1209
System.Web.Mvc.DefaultModelBinder.BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +333
System.Web.Mvc.ControllerActionInvoker.GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor) +343
System.Web.Mvc.ControllerActionInvoker.GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor) +105
System.Web.Mvc.Async.<>c__DisplayClass3_1.<BeginInvokeAction>b__0(AsyncCallback asyncCallback, Object asyncState) +640
System.Web.Mvc.Async.WrappedAsyncResult`1.CallBeginDelegate(AsyncCallback callback, Object callbackState) +14
System.Web.Mvc.Async.WrappedAsyncResultBase`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +128
System.Web.Mvc.Async.AsyncControllerActionInvoker.BeginInvokeAction(ControllerContext controllerContext, String actionName, AsyncCallback callback, Object state) +346
System.Web.Mvc.<>c.<BeginExecuteCore>b__152_0(AsyncCallback asyncCallback, Object asyncState, ExecuteCoreState innerState) +27
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallBeginDelegate(AsyncCallback callback, Object callbackState) +30
System.Web.Mvc.Async.WrappedAsyncResultBase`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +128
System.Web.Mvc.Controller.BeginExecuteCore(AsyncCallback callback, Object state) +494
System.Web.Mvc.<>c.<BeginExecute>b__151_1(AsyncCallback asyncCallback, Object callbackState, Controller controller) +16
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallBeginDelegate(AsyncCallback callback, Object callbackState) +20
System.Web.Mvc.Async.WrappedAsyncResultBase`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +128
System.Web.Mvc.Controller.BeginExecute(RequestContext requestContext, AsyncCallback callback, Object state) +403
System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.BeginExecute(RequestContext requestContext, AsyncCallback callback, Object state) +16
System.Web.Mvc.<>c.<BeginProcessRequest>b__20_0(AsyncCallback asyncCallback, Object asyncState, ProcessRequestState innerState) +54
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallBeginDelegate(AsyncCallback callback, Object callbackState) +30
System.Web.Mvc.Async.WrappedAsyncResultBase`1.Begin(AsyncCallback callback, Object state, Int32 timeout) +128
System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +427
System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state) +48
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +16
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +103
System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) +48
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +159
Thank you!