OleDbDataAdapter da = new OleDbDataAdapter( "exec GetMaterials "  + _ID.ToString(),DBSupport.Connection);
da.Fill(Table);
^^^^^^^^

[InvalidOperationException: ExecuteReader requires an open and available Connection. The connection's current state is Open, Executing.]
   System.Data.OleDb.OleDbConnection.SetStateExecuting(OleDbCommand attempt, String method, Boolean flag) + 143 
   System.Data.OleDb.OleDbCommand.ValidateConnectionAndTransaction(String method, Int32& localState) + 103 
   System.Data.OleDb.OleDbCommand.ExecuteReaderInternal(CommandBehavior behavior, String method) + 61 
   System.Data.OleDb.OleDbCommand.ExecuteReader(CommandBehavior behavior) + 57 
   System.Data.OleDb.OleDbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior) + 5 
   System.Data.Common.DbDataAdapter.Fill(Object data, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) + 121 
   System.Data.Common.DbDataAdapter.Fill(DataTable dataTable, IDbCommand command, CommandBehavior behavior) + 28 
   System.Data.Common.DbDataAdapter.Fill(DataTable dataTable) + 88