Using LIKE in sp_executesql

Question

SET @whereCond = @whereCond + ' AND name LIKE ''%'' + @name + ''%'''

Is there something wrong here? After I generate where condition, I execute it with sp_executesql, but I did get anything. When I SELECT the same thing without sp, it's ok.

How to use LIKE in sp_executesql? Can you bring some examples, please?

Thank you.

UPDATE

declare @name nvarchar(50)

set @name = 'a'

SELECT *
    FROM Tbl_Persons WHERE 1 = 1  AND lastname LIKE '%a%' 

exec sp_executesql 
  N'SELECT *
    FROM Tbl_Persons WHERE 1 = 1  AND lastname LIKE ''%@name%''', 
  N'@name nvarchar(50)',
  @name=@name

First query returns values, second one doesn't return anything.

What's the difference?

Answer 1

The following works for me

declare @name varchar(50)

set @name = 'WAITFOR'


exec sp_executesql 
  N'select * from sys.messages WHERE text  LIKE ''%'' + @name + ''%''', 
  N'@name varchar(50)',
  @name=@name

I think the problem must lie elsewhere.

Edit: Following your update you need to use

exec sp_executesql 
  N'SET @name = ''%'' + @name + ''%'';
    SELECT *
    FROM Tbl_Persons WHERE 1 = 1  AND lastname LIKE @name', 
  N'@name nvarchar(50)',
  @name=@name

As it stands you are searching for text containing the actual substring @name