將“ WHERE”查詢與LINQ結合

Question

在常規SQL中，我可以編寫一個查詢，例如

select * from geocodes where NAME='somename' and STATE='somestate'

但是在LINQ中，我不知道該怎么做。 我想為我使用LINQ的以下單個查詢編寫一些組合查詢：

if (!String.IsNullOrEmpty(searchString))
        {
            switch (searchBy)
            {
                case "Name":
                    geocodes = geocodes.Where(s => s.NAME.Contains(searchString));
                    break;
                case "Site":
                    geocodes = geocodes.Where(s => s.CFN_SITE.Contains(searchString));
                    break;
                case "Address":
                    geocodes = geocodes.Where(s => s.STREET1.Contains(searchString));
                    break;
                case "City":
                    geocodes = geocodes.Where(s => s.CITY.Contains(searchString));
                    break;
                case "State":
                    geocodes = geocodes.Where(s => s.STATE_CODE.Contains(searchString));
                    break;
                case "Acct":
                    geocodes = geocodes.Where(s => s.AccountNumber.Contains(searchString));
                    break;
            }

        }

Answer 1

使用&&邏輯AND運算符：

geoCodes = geoCodes.Where(s => s.Name.Contains(someName) && s.State.Contains(someState));

Answer 2

如果geocodes是IQueryable<>則可以利用創建可查詢對象所附帶的延遲執行。 您的代碼可能看起來像這樣：

if(searchByName) //Some boolean value to indicate you are searching the name
{
    geocodes = geocodes.Where(s => s.NAME.Contains(searchString));
}

if(searchBySite)
{
    geocodes = geocodes.Where(s => s.CFN_SITE.Contains(searchString));
}

if(searchByAddress)
{
    geocodes = geocodes.Where(s => s.STREET1.Contains(searchString));
}

//etc...

您的查詢實際上不會發送到數據庫，因為您純粹是在構建它。 僅當您通過枚舉結果（通過調用ToList()或對其進行循環ToList()實現數據時，實體框架才會構建所需的SQL