index was outside the bounds of the array . why?

public List<CategoriesRollup> CategBranch()
{
   var categBranch = new List<CategoriesRollup>();
   const string spName = "categories_rollup_branchlist";
   using (var con = _connectionString.GetConnection())
   using (var cmd = new SqlCommand(spName, con))
   {
      try
      {
         cmd.Parameters.Add("@username", SqlDbType.VarChar).Value = UsersSession.Users.UserName;
         cmd.Parameters.Add("@terminal", SqlDbType.VarChar).Value = IpAddress.GetMyIpAddress();
         cmd.Parameters.Add("@type", SqlDbType.TinyInt).Value = 1;
         cmd.CommandType = CommandType.StoredProcedure;
         var rdr = cmd.ExecuteReader();

         if (rdr.HasRows)
            while (rdr.Read())
               categBranch.Add(new CategoriesRollup
                  {
                     Result = Convert.ToInt32(rdr["result"]),
                     PromoKey = Convert.ToInt32(rdr["Id"]),
                     Branch = rdr["Branch"].ToString(),
                     Combo = rdr["Combo"].ToString(),
                     Category = rdr["Category"].ToString(),
                     Item = rdr["Item"].ToString()
                  });

            cmd.Dispose();
      }

CREATE TABLE #promosPerBranch
(
   id INT IDENTITY (1,1),
   PromoKey int
)
CREATE TABLE #wholebranch (
   Id INT IDENTITY (1,1),
   BranchLookupKey INT,
   Branch VARCHAR(50),
   ComboPromoKey INT,
   Combo VARCHAR(60),
   CategoryKey INT,
   Category VARCHAR(50),
   ItemCategoryKey INT,
   Item VARCHAR(60)
)

INSERT INTO #promosPerBranch
SELECT promo_key AS 'PromoKey' 
FROM dbo.branch_promos 
WHERE branch_lookup_key = branch_lookup_key
SELECT @countPromos = COUNT(*) from #promosPerBranch
SET @startPromos = 1
WHILE @startPromos <= @countPromos
BEGIN
   --SET @id = (SELECT id FROM #wholebranch WHERE Id = (SELECT id FROM #promosPerBranch WHERE id = id)
   --SELECT @id = id FROM #wholebranch WHERE id = Id
   SELECT @branch_code = branch_code FROM dbo.branches WHERE lookup_key = @promoKey
   SELECT @promoKey = promoKey FROM #promosPerBranch WHERE id = @startPromos
   SELECT @categoryKeys = p.category_keys FROM dbo.promos p WHERE [key] = @promoKey
   INSERT INTO #wholebranch
   SELECT  
      --b.[key] AS 'BranchKey',
      b.lookup_key AS 'BranchLookupKey',
      b.branch_code AS 'Branch',
      p.[key] AS 'ComboPromoKey',
      p.name AS 'Combo',
      c.[key] AS 'CategoryKey',
      c.name AS 'Category',
      i.category_key AS 'ItemCategoryKey',
      i.name AS 'Item'
		 
      FROM items i 
         INNER JOIN dbo.branches b ON i.category_key = b.lookup_key
         INNER JOIN dbo.categories c ON i.category_key = c.[key]  
         INNER JOIN dbo.promos p ON p.[key] = @promoKey
         WHERE category_key IN (SELECT [key] FROM dbo.categories
         WHERE [key] IN (SELECT * FROM dbo.parse_comma_delimited_string(@categoryKeys)))
   SET @startPromos = @startPromos + 1
END