I can't speak French but I can tell you where the problems are in your code. First is the procedure declaration. You were missing parenthesis around your parmeters. Second issue is the code after your procedure. You were missing the single quotes around your xml.

Here are the two pieces with valid syntax.

CREATE PROCEDURE [dbo].[SP_CLR_Export_Excel]

(

-- Add the parameters for the stored procedure here

@proc [nvarchar](100),

@path [nvarchar](200),

@filename [nvarchar](100),

@params xml

)AS EXTERNAL NAME SP_CLR_ExportToExcel.StoredProcedure.ExportToExcel

GO

DECLARE @path varchar(4000),

@file varchar(4000),

@params XML

SET @path = 'C:\XLS\'

SET @file = 'MonfichierExcel'

-- les Paramètres de la procédure appelées

SET @params = '<params> <param name="@pUserID" value="null ">

<param name="@pDepartmentID" value="null ">

<param name="@pStartDate" value="null ">

<param name="@pEndDate" value="null "> </params>'

EXECUTE SP_CLR_Export_Excel 'dbo.DetailRaport', @path, @file, @params;

GO