Concatenation in stored procedure

hi everyone
i am writing a stored procedure and i am new in this field
i want to concatenate a string, i got an error
hope someone could help.
my stored procedure is:
CREATE PROCEDURE dbo.ProdCatComp
(
@.Product nvarchar(40),
)
AS
DECLARE @.str nvarchar(100)
SET @.str='Products.ProductName like '%' + @.Product + '%''

SELECT Products.ProductName, Products.UnitPrice, Categories.CategoryName, Suppliers.CompanyName, Suppliers.ContactName, Suppliers.HomePage
FROM Products INNER JOIN
Suppliers ON Products.SupplierID = Suppliers.SupplierID INNER JOIN
Categories ON Products.CategoryID = Categories.CategoryID
WHERE Products.ProductName<>'' AND @.str
GO

The error is :
Error 403: Invalid operator for data type. Operator equals modulo, type equals varchar.you have to make the whole query dynamic
and then use exec/sp_executesql|||luber is correct in most cases you will need to build a sql string and then execute it, but in this particular case the code below should work - not tested.

CREATE PROCEDURE dbo.ProdCatComp
 @.Product nvarchar(40)
AS
 DECLARE @.str nvarchar(100)
 SET @.str = '%' + @.Product + '%'
 SELECT Products.ProductName,
 Products.UnitPrice,
 Categories.CategoryName,
 Suppliers.CompanyName,
 Suppliers.ContactName,
 Suppliers.HomePage
 FROM Products
 INNER JOIN Suppliers
 ON Products.SupplierID = Suppliers.SupplierID
 INNER JOIN Categories
 ON Products.CategoryID = Categories.CategoryID
 WHERE Products.ProductName <> ''
 AND Products.ProductName LIKE @.str
GO