C# 3.0入門系列（十一）-之In, Like操作(2)

上面的%是通配符，表示，該字段含有某個值，不知道的位置使用%代替。第一個是表示中間一段是AD，兩頭不清楚。第二個是結尾是AD,前面的不清楚。第三個相反，開頭是AD，結尾不清楚。其對應的Linq 語句為

var q = (from c in db.Customers
where c.CustomerID.Contains("ROUT")
select c).ToList();

其生成的sql為

SELECT [t0].[CustomerID], [t0].[CompanyName], [t0].[ContactName], [t0].[ContactT
itle], [t0].[Address], [t0].[City], [t0].[Region], [t0].[PostalCode], [t0].[Coun
try], [t0].[Phone], [t0].[Fax]
FROM [dbo].[Customers] AS [t0]
WHERE [t0].[CustomerID] LIKE @p0
-- @p0: Input String (Size = 6; Prec = 0; Scale = 0) [%ROUT%]

以ISSA結尾,頭部通配：

var q = (from c in db.Customers
where c.CustomerID.EndsWith("ISSA")
select c).ToList();

其生成的sql為

SELECT [t0].[CustomerID], [t0].[CompanyName], [t0].[ContactName], [t0].[ContactT
itle], [t0].[Address], [t0].[City], [t0].[Region], [t0].[PostalCode], [t0].[Coun
try], [t0].[Phone], [t0].[Fax]
FROM [dbo].[Customers] AS [t0]
WHERE [t0].[CustomerID] LIKE @p0
-- @p0: Input String (Size = 5; Prec = 0; Scale = 0) [%ISSA]

以ARO開始，尾部通配：

var q = (from c in db.Customers
where c.CustomerID.StartsWith("ARO")
select c).ToList();

其生成的sql為

SELECT [t0].[CustomerID], [t0].[CompanyName], [t0].[ContactName], [t0].[ContactT
itle], [t0].[Address], [t0].[City], [t0].[Region], [t0].[PostalCode], [t0].[Coun
try], [t0].[Phone], [t0].[Fax]
FROM [dbo].[Customers] AS [t0]
WHERE [t0].[CustomerID] LIKE @p0
-- @p0: Input String (Size = 4; Prec = 0; Scale = 0) [ARO%]

Linq 還提供了一種方法，叫做SqlMethods.Like，需要先添加System.Data.Linq.SqlClIEnt名稱空間。上面的三個可以寫成

var q = (from c in db.Customers
where SqlMethods.Like(c.CustomerID, "%ROUT%")
select c).ToList();

這裡，你需要自己填寫通配符，告訴Linq你是如何匹配。比如

var q = (from c in db.Customers
where SqlMethods.Like(c.CustomerID, "%ISSA")
select c).ToList();