TOPIC:

I am trying to save TRxMemoryData to file as following but I am getting error "There is no TDatapacketReaderClass registered for this kind of data-stream". Please see attached screenshot.
SaveToFile(FileName, dxXML) - same error
SaveToFile(FileName, dxAny) - same error
SaveToFile(FileName) - same error

pl_RX don't has TDataPacketReader class for XML export

You must use (or modify)
codetyphon\fpcsrc\packages\fcl-db\src\base\xmldatapacketreader.pp
XMLDatapacketReader unit
has and register the TXMLDatapacketReader = class(TDataPacketReader)

Please have a Look and at these:
codetyphon\fpcsrc\packages\fcl-db\src\base\csvdataset.pp
pl_PascalSCADA\source\database\fpsbufdataset.pas
pl_ZMSQL\source\zmbufdataset.pas

I added XMLDatapacketReader on uses but still got same error

Please give us more info
for your project

All I am trying to store some data in TRxMemoryData and load it. It's not so special, just simple save and load. But now I can't save it. Below is my TRxMemoryData stucture:
with TableExtract do
begin
with FieldDefs.AddFieldDef do
begin
DataType := ftInteger;
Name := 'ID';
end;
with FieldDefs.AddFieldDef do
begin
DataType := ftString;
Size := 12;
Name := 'DatabaseType';
end;
with FieldDefs.AddFieldDef do
begin
DataType := ftString;
Size := 200;
Name := 'TableName';
end;
end;

with FieldExtract do
begin
with FieldDefs.AddFieldDef do
begin
DataType := ftString;
Size := 1;
Name := 'TableType';
end;
with FieldDefs.AddFieldDef do
begin
DataType := ftString;
Size := 200;
Name := 'TableName';
end;
with FieldDefs.AddFieldDef do
begin
DataType := ftString;
Size := 200;
Name := 'FieldName';
end;
with FieldDefs.AddFieldDef do
begin
DataType := ftString;
Size := 20;
Name := 'FieldType';
end;
with FieldDefs.AddFieldDef do
begin
DataType := ftInteger;
Name := 'FieldSize';
end;
with FieldDefs.AddFieldDef do
begin
DataType := ftString;
Size := 8;
Name := 'FieldNullable';
end;
with FieldDefs.AddFieldDef do
begin
DataType := ftString;
Size := 20;
Name := 'FieldDataType';
end;
end;