SQLクエリの変換LINQ

Question

SQLクエリをLINQに変換する際に問題があります。どのようにLINQ where節でcaseステートメントを作成しますか？ここに私の現在のSQLクエリがあります。

ALTER PROCEDURE [dbo].[CustomerBySearch] 

@FirstName VARCHAR(255) = '', 
@LastName VARCHAR(255) = '', 
@Email VARCHAR(255) = '', 
@Phone VARCHAR(30) = '' 

AS 
BEGIN 

SELECT  CustomerId, 
      Title, 
      FirstName, 
      LastName, 
      RegistrationDate, 
      DayPhone, 
      Mobile, 
      LoginEmail 
FROM  CustomerInfo 
HAVING  CASE WHEN @FirstName = '' THEN @FirstName ELSE FirstName END Like @FirstName + '%' 
      AND 
      CASE WHEN @LastName = '' THEN @LastName ELSE LastName END Like @LastName + '%' 
      AND 
      CASE WHEN @Email = '' THEN @Email ELSE LoginEmail END Like @Email 
      AND 
      (
       CASE WHEN @Phone = '' THEN @Phone ELSE DayPhone END LIKE '%' + @Phone 
       OR 
       CASE WHEN @Phone = '' THEN @Phone ELSE Mobile END LIKE '%' + @Phone 
      ) 
ORDER BY CustomerId DESC 
END 

Answer 1

これは何らかのフィルタオプション機能ですか？ LINQので

もしそうなら、このようなものは、LINQで動作するはずです...

var infos = customerInfos; 

if(!string.IsNullOfEmpty(firstname)) 
    infos = infos.Where(i => i.FirstName.Contains(firstname)); 
if(!string.IsNullOfEmpty(lastname)) 
    infos = infos.Where(i => i.LastName.Contains(lastname)); 
if(!string.IsNullOfEmpty(email)) 
    infos = infos.Where(i => i.Email.Contains(email)); 
if(!string.IsNullOfEmpty(phone)) 
    infos = infos.Where(i => i.DayPhone.Contains(phone) || i.Mobile.Contains(phone)); 

infos = infos.OrderByDescending(i => i.CustomerId); 

Answer 2

、私は次のようなものを使用して、これを構築したい：

var query = db.CustomerInfo; 

if (!string.IsNullOrEqual(firstName)) 
    query = query.Where(x => x.FirstName.StartsWith(firstName)); 

// similar if statements for lastname, email and phone, each one building on the existing query 

return query.OrderBy(x => x.CustomerId);