SqlClient Xml Output parameter "was not supplied"

I receive an SqlException when running the following code.

"Procedure or function 'usp_Search' expects parameter '@pxmlSearchOutput', which was not supplied."

My parameters + request.

    using (var connection = new SqlConnection(_connectionString))
    {
        using (var command = new SqlCommand("Search.usp_Search", con))
        {

            var pxmlSearchOutput = new SqlParameter();
            pxmlSearchOutput.ParameterName = "@pxmlSearchOutput";
            pxmlSearchOutput.SqlDbType = SqlDbType.Xml;
            pxmlSearchOutput.Direction = ParameterDirection.Output;
            pxmlSearchOutput.Size = 1;
            command.Parameters.Add(pxmlSearchOutput);

            var pxmlSearchInput = new SqlParameter();
            pxmlSearchInput.ParameterName = "@pxmlSearchInput";
            pxmlSearchInput.Value = requestXML;//is valid xml, is a local var
            pxmlSearchInput.SqlDbType = SqlDbType.Xml;
            command.Parameters.Add(pxmlSearchInput);

            var pbitDebug = new SqlParameter();
            pbitDebug.Value = false;
            pbitDebug.ParameterName = "@pbitDebug";
            pbitDebug.SqlDbType = SqlDbType.Bit;
            com开发者_如何学Gomand.Parameters.Add(pbitDebug);

            var pintErrorNumber = new SqlParameter();
            pintErrorNumber.ParameterName = "@pintErrorNumber";
            pintErrorNumber.SqlDbType = SqlDbType.Int;
            pintErrorNumber.Direction = ParameterDirection.Output;
            command.Parameters.Add(pintErrorNumber);

            connection.Open();
            command.ExecuteScalar();
            connection.Close();
        }
    }

Using sql profiler, I can extract the following:

        declare @p3 xml
        set @p3=null
        declare @p4 xml
        set @p4=convert(xml,'***Redacted - This is however, valid xml, which convert works on happily***')
        declare @p6 int
        set @p6=NULL
        exec 
        sp_executesql 
        N'Search.usp_Search',
        N'@pxmlSearchOutput xml output,@pxmlSearchInput xml,@pbitDebug bit,@pintErrorNumber int output',
        @pxmlSearchOutput=@p3 output,
        @pxmlSearchInput=@p4,
        @pbitDebug=0,
        @pintErrorNumber=@p6 output
        select @p3, @p6

I am unable to diagnose exactly what is wrong with the SQL (and thus, how it relates to the .net code). Any ideas?

You execute the batch, a request of type Text:

Search.usp_Search

You do pass a bunch of parameters to this batch, but those are all ignored as they aren't actually used in the batch itself. You have two alternatives:

• use the parameters passed to the batch in the batch itself: var command = new SqlCommand("exec Search.usp_Search @pxmlSearchOutput output, @pxmlSearchInput,@pbitDebug, @pintErrorNumber output", con))
• Tell ADO.NEt that you are making an RPC call, not merely executing a batch: command.CommandType = CommandType.StoredProcedure;

Either change will work (but not both).