方法＆＃39; Union＆＃39;不受支持。声明类型：System.Linq.Queryable（C＃）

Question

我需要合并两个IQueryables。这是我的代码：

IQueryable<SearchResultsItem> resourceQueriable = GetIndexQueriable(ResourceIndexName);
IQueryable<SearchResultsItem> resourceQueriableResults = resourceQueriable.Where(x => x.DatabaseName == Database);

IQueryable<SearchResultsItem> resourcePageQueriable = GetIndexQueriable(ResourcePageIndexName);
IQueryable<SearchResultsItem> resourcePageQueriableResults =
    resourcePageQueriable.Where(x => x.DatabaseName == Database);

string ResourceTypeGuid = ItemReference.ItemReference.BBB_ResourceTypes_ProductGuide.InnerItem.ID.ToString().ConvertToShortId();

resourceQueriableResults = resourceQueriableResults.Where(x => x.ResourceType == ResourceTypeGuid);
resourcePageQueriableResults = resourcePageQueriableResults.Where(x => Boolean.Parse(x.IncludeInGuides));

IQueryable<SearchResultsItem> concatResults = resourceQueriableResults.Union(resourcePageQueriableResults);

IEnumerable<KeyValuePair<string, string>> namePathPairs =
    concatResults
        .Where(x => x.DatabaseName == Database)
        .OrderBy(y => y.NavTitle)
        .ToList() //Enumerate the query before translating it.
        .Select(x => new KeyValuePair<string, string>(x.NavTitle.CleanNavTitle(), x.Url));

return namePathPairs;

错误发生在IEnumerable<KeyValuePair<string, string>> namePathPairs = concatResults....

上

为什么会抛出此错误，如何合并我的两个IQueryables？我之前只有一个IQueryable，这很好用

IEnumerable<KeyValuePair<string, string>> namePathPairs =
            resourceQueriable
                .Where(x => x.DatabaseName == Database)
                .OrderBy(y => y.NavTitle)
                .ToList() //Enumerate the query before translating it.
                .Select(x => new KeyValuePair<string, string>(x.NavTitle.CleanNavTitle(), x.Url));

但是现在我在该行上使用了合并的IQueryable，它无法正常工作。