Use sp_executesql to deal with the Image type Parameter in SP

What I want is to realise this StoreProcedure. When execute the SP, if the parameter is not null then update the correspond fields or else keep it as original value. Everybody knows that I should use dynamic SQL. I agree with it. However, here is the problem. If the field type is Char we can set up a SQL sentence like this
SET @sql = @sql + ' Phone = ''' + @phone  + ''''

But what if the field type is Image, we can't write it in the same way.
SET @sql = ' set IMAGE = ' + @image
it will raise an error tell you that the @image parameter is not char type. That's true. How can we deal with it?
I look up many resource and get this down.
Use sp_executesql. It is a build-in SP in SQL Server. This SP support parameters replacement. For more detail, please get it from MSDN. I will show an example as follows

 

ALTER   PROCEDURE   [ dbo ] . [ UpdateSP ]  
     --  Add the parameters for the stored procedure here
@myName   NVARCHAR ( 50 ),
@image   IMAGE ,
@phone   NVARCHAR ( 50 )
AS
BEGIN
DECLARE   @sql   NVARCHAR ( MAX )
DECLARE   @imgParameter   NVARCHAR ( 50 )
     --  SET NOCOUNT ON added to prevent extra result sets from
     --  interfering with SELECT statements.
     SET  NOCOUNT  ON ;
     SET   @sql   =   '' ;
    
    
     IF   @image   is   not   NULL
     BEGIN
         SET   @sql   =   '  set IMAGE = @image '   
     END
    
     SET   @imgParameter   =  N ' @image IMAGE '

     IF   @phone   IS   NOT   NULL
     BEGIN
         IF   @sql   <>   ''
             SET   @sql   =   @sql   +   '  ,  '
         ELSE
             SET   @sql   =   @sql   +   '  SET  '
         SET   @sql   =   @sql   +   '  Phone =  '''   +   @phone    +   ''''
     END
    
    
     if   @sql   <>   ''
     BEGIN
         SET   @sql   =   ' UPDATE MyTbl  '   +   @sql   +   '  WHERE MyName =  '''   +   @myName   +   ''''
         Exec  sp_executesql  @sql , @imgParameter , @image
     END
     ELSE
     BEGIN
         PRINT   ' EMPTY '
     END
END