Problem Getting Recoreds From Store Proedure Between Dates...

i have a gridView and i want to get the recoreds between specific dates.. so i put two calendars to select the dates...

and they will filter the recoreds..(i seleced dates and it returns non recors and theres recored betwenn those dates and in a SQL View it works )

What can i do? Thanks

Store Proceure Function:

 CREATE PROCEDURE sp_FindTnoaGrid
@SearchTnoa nvarchar(14),
@beginDate as nvarchar(50),
@endDate as nvarchar(50)
AS
-- order by dbo.V_tnuot.t_erech desc--



if (@beginDate='%') or (@endDate='%')
SELECT dbo.V_tnuot.kod_lakoha, dbo.V_tnuot.t_erech, dbo.V_tnuot.t_peula, dbo.V_tnuot.scum_peula as sum,
dbo.V_tnuot.strHpoalimSugKodTnua, dbo.V_tnuot.DescSugPeula, cast(year(cast(@beginDate as datetime)) as nvarchar)+'-'+cast(month(cast(@beginDate as datetime)) as nvarchar)+'-'+cast(day(cast(@beginDate as datetime)) as nvarchar) as try,
dbo.V_tnuot.Hpoalim_HodeshSahar
FROM dbo.V_tnuot LEFT OUTER JOIN
dbo.tblCategTnuot_KodPeula ON dbo.V_tnuot.strHpoalimSugKodTnua = dbo.tblCategTnuot_KodPeula.idKodTnua

WHERE ( kod_lakoha = @SearchTnoa)

if (@beginDate<>'%') and (@endDate<>'%')
SELECT dbo.V_tnuot.kod_lakoha, dbo.V_tnuot.t_erech, dbo.V_tnuot.t_peula, dbo.V_tnuot.scum_peula as sum,
dbo.V_tnuot.strHpoalimSugKodTnua, dbo.V_tnuot.DescSugPeula,
dbo.V_tnuot.Hpoalim_HodeshSahar
FROM dbo.V_tnuot LEFT OUTER JOIN
dbo.tblCategTnuot_KodPeula ON dbo.V_tnuot.strHpoalimSugKodTnua = dbo.tblCategTnuot_KodPeula.idKodTnua

WHERE ( kod_lakoha = @SearchTnoa) and (dbo.V_tnuot.t_peula BETWEEN cast(@beginDate as datetime) and cast(@endDate as datetime) )
GO