add "N" to command Parameters

[StrangerInBeijing]

as you can see in this post, I HAVE to add N in front of my varible to search on japanese or chinese.

calling the following sproc from the QA works fine like this:
TESTGETCAPLCO 'ja-JP', N'上海'
(whereas TESTGETCAPLCO 'ja-JP', '上海') will return no results.

But I want to call this stored procedure from my code. How do I add this N? I tried so many things allready, like "N" + keyword, etc:
C# Code

comm = new SqlCommand("TESTGETCAPLCO", this.conn);
comm.Parameters.Add("@lang", SqlDbType.NVarChar, 10).Value			= lang;
comm.Parameters.Add("@keyword", SqlDbType.NVarChar, 255).Value		= keyword;
comm.CommandType = CommandType.StoredProcedure;
SqlDataReader reader;
try
{
	reader = comm.ExecuteReader();

STORED PROCEDURE:

alter proc TESTGETCAPLCO
@lang		NVARCHAR(10),
@keyword	NVARCHAR(255)
AS
set @keyword =  '%' + @keyword + '%'
SELECT ID,
CASE 
	WHEN @lang = 'en-US' THEN coName_en
	WHEN @lang = 'ja-JP' THEN coName_ja
	WHEN @lang = 'zh-CN' THEN coName_zh
END
AS coName
FROM tblCAPLCompanies
WHERE 
CASE 
	WHEN @lang = 'en-US' THEN coName_en
	WHEN @lang = 'ja-JP' THEN coName_ja
	WHEN @lang = 'zh-CN' THEN coName_zh 
END
LIKE  @keyword