debug user defined function in visual studio 2015

I am trying to debug a sql user defined function


I created a stored proc  

ALTER PROCEDURE [dbo].[sp_call_bcp_function]
      -- Add the parameters for the stored procedure here
      
AS
BEGIN
      
      -- Add the parameters for the function here
      Declare @servername varchar(50)
      declare @databasename varchar(50)
      Declare @tablename varchar(500)
      Declare @FullFilePath varchar(1000)
      declare @IncludeColumnHeaders varchar(1)
      Declare @WhereClause varchar(1000)        
      
        set  @servername = 'GVCBA'
      set @databasename = 'MarketingDirectMailLists'
      set  @tablename = 'vDirectMail_Welcome_MailHouseFile'

      set @FullFilePath = '\\gvcba\Marketing\DirectMail\2017\May\Welcome\Mailhouse\Welcome_2017_May_2017_04_24_Time_16_29_MailHouse_790.csv'

      set @IncludeColumnHeaders= 'Y'       

set @WhereClause = 'where campaignid = 381'


      SELECT dbo.fnBuildBCPStatement(@servername, @databasename, @tablename, @FullFilePath, @IncludeColumnHeaders, @WhereClause) as BCPSQL



The function  is concatenating column names into a variable named @sql which is defined as

DECLARE @Sql varchar(max)




      DECLARE BCP_FieldNames_cursor_pass1 CURSOR
                                    FOR SELECT column_name,data_type FROM INFORMATION_SCHEMA.COLUMNS where table_name = @tablename
                        end      


                  OPEN BCP_FieldNames_cursor_pass1

                  FETCH NEXT FROM BCP_FieldNames_cursor_pass1 into  @ColumnName,@DataType;
                  SET @Sql = 'bcp "select '
                  WHILE @@FETCH_STATUS = 0
                        BEGIN
        
                                                      SET @Sql += char(39) +  convert(varchar(1000),@ColumnName)  + char(39) + ','
                        

                          FETCH NEXT FROM BCP_FieldNames_cursor_pass1 into  @ColumnName,@DataType;
                        END

If I put a break point and look at value of @sql, it only has 255 characters

if I run the entire stored proc with no break points in debug.    I get almost 2000 characters

anybody have an idea why???????

only difference is whether breakpoint is set or not

Driving me nuts