SQL Server 2012 :: CLR Procedure Takes Ages To Pass TVP To Stored Procedure?

On SQL 2012 (64bit) I have a CLR stored procedure that calls another, T-SQL stored procedure.

The CLR procedure passes a sizeable amount of data via a user defined table type resp.table values parameter. It passes about 12,000 rows with 3 columns each.

For some reason the call of the procedure is verz very slow. I mean just the call, not the procedure.

I changed the procdure to do nothing (return 1 in first line).

So with all parameters set from

command.ExecuteNonQuery()to
create proc usp_Proc1
@myTable myTable read only
begin
return 1
end

it takes 8 seconds.I measured all other steps (creating the data table in CLR, creating the SQL Param, adding it to the command, executing the stored procedure) and all of them work fine and very fast.

When I trace the procedure call in SQL Profiler I get a line like this for each line of the data table (12,000)

SP:StmtCompleted -- Encrypted Text.

As I said, not the procedure or the creation of the data table takes so long, really only the passing of the data table to the procedure.