I have problem with my umbraco 7.10.0 assembly: 1.0.6659.16870 site. it sometimes shows 500 error. An item with the same key has already been added.

if (CurrentPage.HasValue("dePage"))
{
    ICollection<Umbraco.Core.Models.IPublishedContent> deList = CurrentPage.dePage;
    foreach (var item in deList)
    {
        deurl = item.Url;
    }
}

the Error in this line

 ICollection<Umbraco.Core.Models.IPublishedContent> deList = CurrentPage.dePage;

[ArgumentException: An item with the same key has already been added.] System.ThrowHelper.ThrowArgumentException(ExceptionResource resource) +52 System.Collections.Generic.Dictionary2.Insert(TKey key, TValue value, Boolean add) +183 Umbraco.Core.Services.IdkMap.Populate(IEnumerable1 pairs, UmbracoObjectTypes umbracoObjectType) in D:\a\1\s\src\Umbraco.Core\Services\IdkMap.cs:79 Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedContentCache.EnsureIdkMap(UmbracoContext umbracoContext) in D:\a\1\s\src\Umbraco.Web\PublishedCache\XmlPublishedCache\PublishedContentCache.cs:369 Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedContentCache.GetById(UmbracoContext umbracoContext, Boolean preview, Guid nodeKey) in D:\a\1\s\src\Umbraco.Web\PublishedCache\XmlPublishedCache\PublishedContentCache.cs:427 Umbraco.Web.PublishedCache.ContextualPublishedContentCache.GetById(Boolean preview, Guid contentKey) in D:\a\1\s\src\Umbraco.Web\PublishedCache\ContextualPublishedContentCache.cs:27 Umbraco.Web.PublishedContentQuery.TypedContent(Guid id) in D:\a\1\s\src\Umbraco.Web\PublishedContentQuery.cs:70 Umbraco.Web.PublishedContentQueryExtensions.TypedContent(ITypedPublishedContentQuery contentQuery, Udi id) in D:\a\1\s\src\Umbraco.Web\PublishedContentQueryExtensions.cs:18 Umbraco.Web.UmbracoHelper.TypedContent(Udi id) in D:\a\1\s\src\Umbraco.Web\UmbracoHelper.cs:639 Umbraco.Web.PropertyEditors.ValueConverters.MultiNodeTreePickerPropertyConverter.GetPublishedContent(T nodeId, UmbracoObjectTypes& actualType, UmbracoObjectTypes expectedType, Func2 contentFetcher) in D:\a\1\s\src\Umbraco.Web\PropertyEditors\ValueConverters\MultiNodeTreePickerPropertyConverter.cs:207 Umbraco.Web.PropertyEditors.ValueConverters.MultiNodeTreePickerPropertyConverter.ConvertSourceToObject(PublishedPropertyType propertyType, Object source, Boolean preview) in D:\a\1\s\src\Umbraco.Web\PropertyEditors\ValueConverters\MultiNodeTreePickerPropertyConverter.cs:170 Umbraco.Web.PublishedCache.XmlPublishedCache.XmlPublishedProperty.get_Value() in D:\a\1\s\src\Umbraco.Web\PublishedCache\XmlPublishedCache\XmlPublishedProperty.cs:51 Umbraco.Web.Models.DynamicPublishedContent.TryGetUserProperty(GetMemberBinder binder) in D:\a\1\s\src\Umbraco.Web\Models\DynamicPublishedContent.cs:202 Umbraco.Web.Models.<>c__DisplayClass22_0.<TryGetMember>b__0(Func2 m) in D:\a\1\s\src\Umbraco.Web\Models\DynamicPublishedContent.cs:256 System.Linq.WhereSelectListIterator2.MoveNext() +99 System.Linq.WhereEnumerableIterator1.MoveNext() +209 Umbraco.Web.Models.DynamicPublishedContent.TryGetMember(GetMemberBinder binder, Object& result) in D:\a\1\s\src\Umbraco.Web\Models\DynamicPublishedContent.cs:255 CallSite.Target(Closure , CallSite , Object ) +159 System.Dynamic.UpdateDelegates.UpdateAndExecute1(CallSite site, T0 arg0) +629 ASP.PageViewsPartialsEnDeHeadercshtml.Execute() in c:\Inetpub\vhosts\ahmad-osman.com\MySite\Views\Partials\EnDeHeader.cshtml:10 System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +198 System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +105 System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +90 System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +235 System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +107 Umbraco.Core.Profiling.ProfilingView.Render(ViewContext viewContext, TextWriter writer) in D:\a\1\s\src\Umbraco.Web\Mvc\ProfilingView.cs:24 System.Web.Mvc.HtmlHelper.RenderPartialInternal(String partialViewName, ViewDataDictionary viewData, Object model, TextWriter writer, ViewEngineCollection viewEngineCollection) +277 System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model, ViewDataDictionary viewData) +91 System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName) +32 ASP.PageViewsSitecshtml.Execute() in c:\Inetpub\vhosts\ahmad-osman.com\MySite\Views\Site.cshtml:187 System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +198 System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +105 System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +90 System.Web.WebPages.<>cDisplayClass3.2(TextWriter writer) +232 System.Web.WebPages.HelperResult.WriteTo(TextWriter writer) +10 System.Web.WebPages.WebPageBase.Write(HelperResult result) +80 System.Web.WebPages.WebPageBase.RenderSurrounding(String partialViewName, Action1 body) +63 System.Web.WebPages.WebPageBase.PopContext() +237 System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +98 System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +235 System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +107 Umbraco.Core.Profiling.ProfilingView.Render(ViewContext viewContext, TextWriter writer) in D:\a\1\s\src\Umbraco.Web\Mvc\ProfilingView.cs:24 System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +290 System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +13 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +56 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +420 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +420 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +420 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList1 filters, ActionResult actionResult) +52 System.Web.Mvc.Async.<>cDisplayClass2b.1c() +173 System.Web.Mvc.Async.<>cDisplayClass21.1e(IAsyncResult asyncResult) +100 System.Web.Mvc.Async.WrappedAsyncResult1.CallEndDelegate(IAsyncResult asyncResult) +10 System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +49 System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +27 System.Web.Mvc.Controller._5(IAsyncResult asyncResult, ProcessRequestState innerState) +21 System.Web.Mvc.Async.WrappedAsyncVoid1.CallEndDelegate(IAsyncResult asyncResult) +29 System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +49 System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +28 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9749889 System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) +48 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +159 Any help, please