Timeout Error in Stored Procedure in C#

i have this stored procedure to retreave data from database (dynamic query). and i am calling this stored procedure from c# codebehind, i am passsing two parameters from c# to this stored procedure.

alter procedure [dbo].[GetCompleteCPTDetails]
    @Practice_Short_Name varchar(50),
    @Uploaded_Date nvarchar(max)
as
begin
DECLARE @CPTtablename nvarchar(300)
DECLARE @vQuery NVARCHAR(max)
DECLARE @upldate nvarchar(100)
set @upldate = @Uploaded_Date
set @CPTtablename ='ACER_CLAIMS_MASTER_DETAIL_Hist_'+@Practice_Short_Name
SET @vQuery = 'select Practice_Short_Name,Service_Date_From,Carrier_Name,
   Location_Description,Patient_Number,Patient_First_Name,
   Patient_Last_Name,Voucher_Number,Procedure_Code,Service_Fees,
   Service_Payments,Service_Adjustments,Acer_Status,Acer_Allowed_Amount
   from ' +@CPTtablename+' 
   where Uploaded_Date =''' + @upldate + ''' 
   order by acer_status asc, Service_Date_From desc, Patient_First_Name asc'
EXEC (@vQuery)

end
GO

but when i am running this query it is giving me TimeOut error. but if i assign value to my parameters in SP and Run SP from query windows then it is showing correct data.

can any please explain me why it is giving timeout error if i am calling it from C# codebehind.