c# - Stored procedure returning incorrect ID guid -

i need little this. stored procedure below doesn't seem ever match exiting unique identifier

alter procedure [dbo].[spinsertupdatethisstuff]     @id uniqueidentifier output,     @content nvarchar(255) begin     set nocount on;      declare @taudit table (id uniqueidentifier)      if exists(select * [dbo].[mydata] [id] = @id)     --  update     begin         update [dbo].[mydata]          set [id] = @id,             [content] = @content         output inserted.[id] @taudit         [id] = @id          select id @taudit     end     else     begin         --  insert         set @id = newid()          insert [dbo].cbdata ([id], [content])         output inserted.[id] @taudit         values(@id, @content)          select id @taudit     end;      set @id = (select id @taudit); end 

the c#

cmd.parameters.add("@id", sqldbtype.uniqueidentifier).value = (currentrecord.id == null) ? guid.empty : currentrecord.id; cmd.parameters["@id"].direction = parameterdirection.output; cmd.executenonquery(); currentrecord.id = guid.parse(cmd.parameters["@id"].value.tostring()); 

it seems first if statement not ever become true, if test (select * [dbo].[mydata] [id] = @id) matching uid comes data.

this statement problematic,,

 declare @taudit table (id uniqueidentifier)     if exists(select * [dbo].[mydata] [id] = @id)     --  update          begin 

@id output parameter , null default , trying check that..

basically newid() won't duplicated,so update part redundant