c# - 使用存储过程时，不能多次枚举查询结果

Question

我正在尝试用存储过程替换 View 以根据关键字搜索结果。但是当我传递一个关键字时它会抛出一个错误

The result of a query cannot be enumerated more than once

但如果关键字留空，它会正常工作。以下是我获取搜索结果的方法。谁能就在这种情况下如何枚举结果提供任何建议？

public IEnumerable <BrandNameToIngredient> GetBrandNameToIngMapResults(string Keyword)
{
    IEnumerable<BrandNameToIngredient> lstBrandNametoIng = from map in DB.USP_BRANDNAME_INGREDIENT_MAP()                                                           
                      select new BrandNameToIngredient
                             {
                                 IngredientBrandNameMapID=map.INGREDIENT_PRODUCT_MAP_ID,                            
                                 BrandName = map.FDA_BRAND_NAME,             //From Table 1              
                                 PFCName = map.PFC_DESC==null?"":map.PFC_DESC,  //From Table 1                        
                                 IngredientName = map.INGREDIENT_NAME,       //From Table 2
                                 HCIngredientName = map.HC_INGREDIENT_NAME,   //From Table 2                              
                                 KeywordfromPage = Keyword
                             };

    if (!string.IsNullOrEmpty(Keyword))
    {
        lstBrandNametoIng = lstBrandNametoIng.Where(x => x.BrandName.ToLower().Contains(x.KeywordfromPage.ToLower())        //Able to get result                                                  
                                                        || x.PFCName.ToLower().Contains(x.KeywordfromPage.ToLower())            //Able to get result

                                                        || x.IngredientName.ToLower().Contains(x.KeywordfromPage.ToLower())     //Error Here
                                                        || x.HCIngredientName.ToLower().Contains(x.KeywordfromPage.ToLower())); //Error Here
    }

    return lstBrandNametoIng;
}

Answer 1

最好先对Query进行操作，最后再返回可枚举。

public IEnumerable<BrandNameToIngredient> GetBrandNameToIngMapResults(string Keyword)
{
    var brandNametoIngQuery = DB.USP_BRANDNAME_INGREDIENT_MAP()
                             .Where(x => string.IsNullOrEmpty(Keyword) 
                                        || x.BrandName.Contains(Keyword, StringComparison.OrdinalIgnoreCase)        
                                        || x.PFCName.Contains(Keyword, StringComparison.OrdinalIgnoreCase)           
                                        || x.IngredientName.Contains(Keyword, StringComparison.OrdinalIgnoreCase)     
                                        || x.HCIngredientName.Contains(Keyword, StringComparison.OrdinalIgnoreCase))
                             .Select(map=> new BrandNameToIngredient
                             {
                                  IngredientBrandNameMapID = map.INGREDIENT_PRODUCT_MAP_ID,
                                  BrandName = map.FDA_BRAND_NAME,             //From Table 1              
                                  PFCName = map.PFC_DESC == null ? "" : map.PFC_DESC,  //From Table 1                        
                                  IngredientName = map.INGREDIENT_NAME,       //From Table 2
                                  HCIngredientName = map.HC_INGREDIENT_NAME,   //From Table 2                              
                                  KeywordfromPage = Keyword
                              }).AsEnumerable();
}