SqlCommand scom = new SqlCommand();
scom.Connection = con;
scom.CommandType = CommandType.StoredProcedure;
scom.CommandText = "[SELECT_STORED_PROCEDURE]";
scom.Parameters.Add(new System.Data.SqlClient.SqlParameter("@name", System.Data.SqlDbType.VarChar, 50, System.Data.ParameterDirection.Input, false, ((System.Byte)(0)), ((System.Byte)(0)), "", System.Data.DataRowVersion.Current, null));

scom.Parameters["@name"].Value = name;

где name - некая переменная.