SQL Server Stored Procedure ignores SqlCommand.ParameterCollection

I cannot get a SQL Server 2008R2 stored procedure to acknowledge the VS2008 C# Windows form parameters and return the rows.  If the parametercollection is present, no rows are returned.  If I comment out the parameters, and the stored procedure uses its default values, I get the correct rows returned.

I started with a DataAdapter.Fill approach, but switched to the SqlCommand and SqlDataReader so that I could inspect the objects and values more easily.  When the parameters are Added, I can see the collection of two, and I can see the correct values. I thought using the ampersand in AddWithValue was the problem, so I am adding that in the stored procedure.

Am I missing an obvious step?

thank you,   Jon Angel

                  this.cmdGetRankedScoresheet = new System.Data.SqlClient.SqlCommand();
                   System.Data.DataRow dr;
                    this.sqlConnection1.ConnectionString =
                        System.Configuration.ConfigurationManager.AppSettings["sqlServerConnectionString"].ToString();
                    this.sqlConnection1.Open();
                    this.cmdGetRankedScoresheet.Connection = this.sqlConnection1;
                    this.cmdGetRankedScoresheet.CommandType = CommandType.StoredProcedure;
                    this.cmdGetRankedScoresheet.CommandText = "vsreports.sp_GetRankedScoresheetFinal";
                                        this.cmdGetRankedScoresheet.Parameters.AddWithValue("@GRADE", this.txtPromYear.Text.Substring(2, 2) + "SP");
                    this.cmdGetRankedScoresheet.Parameters.AddWithValue("@BOARD_ID", sBoardType);

                    System.Data.SqlClient.SqlDataReader rdrRankedScoresheet;

                    rdrRankedScoresheet = cmdGetRankedScoresheet.ExecuteReader();
                    while (rdrRankedScoresheet.Read())
                    {
                        dr = this.dsBoards2.Tables["Ranked_Scoresheet_Final_numbers"].NewRow();
                        dr["GRADE"] = rdrRankedScoresheet.GetString(0);
                        dr["BOARD_ID"] = rdrRankedScoresheet.GetString(1);
                        dr["EMPLOYEE_ID"] = rdrRankedScoresheet.GetString(2);
                        dr["PHS_NO"] = rdrRankedScoresheet.GetString(3);
                        dr["Hundred_AVG"] = rdrRankedScoresheet.GetDouble(4);
                        dr["Eightyfive_AVG"] = rdrRankedScoresheet.GetDouble(5);
                        dr["BOARDREC"] = rdrRankedScoresheet.GetString(6);
                        dr["Rank_order"] = rdrRankedScoresheet.GetInt32(7);
                        this.dsBoards2.Tables["Ranked_Scoresheet_Final_numbers"].Rows.Add(dr);

                    }
                    rdrRankedScoresheet.Close();
                    sqlConnection1.Close();
                   dataGrid1.Refresh();

ALTER PROCEDURE [vsreports].[sp_GetRankedScoresheetFinal]
(
	@GRADE nvarchar(3) = 'T',
	@BOARD_ID nvarchar(9) = '15SP'
)
AS
SET NOCOUNT ON;
BEGIN
	OPEN SYMMETRIC KEY CCBPMPIIkey
	DECRYPTION BY CERTIFICATE CCBPMcert;

    DECLARE	@GRADEamp nvarchar(3)
    DECLARE	@BOARD_IDamp nvarchar(9)
   SET @GRADEamp = @GRADE + '%'
   SET @BOARD_IDamp = @BOARD_ID + '%'


SELECT GRADE, BOARD_ID,
CONVERT(VARCHAR(11),  DecryptByKey(EMPLOYEE_ID)) as EMPLOYEE_ID,
CONVERT(NVARCHAR(10), DecryptByKey(PHS_NO)) as PHS_NO,
Hundred_AVG, Eightyfive_AVG, BOARDREC, Rank_order
FROM  dbo.Ranked_Scoresheet_Final_numbers
WHERE GRADE like @GRADEamp and BOARD_ID like @BOARD_IDamp
ORDER BY BOARD_ID, Rank_order
END