Access violation when loading a TClientDataset from XML

VCL
1

Hi

I have a TClientdataset instance that has been saved to a string (using the SaveToStream method).
When I load the string back into another TClientDataset instance I get an access violation in midas.dll at address 0018DDD6, read address 00000000.

The xml I am loading is as follows:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> BillingRunID="21798" FromDateTime="20230831" ToDateTime="20231111T23:59:59999"

Has anyone got any ideas on how to fix this problem.

I am currently running Delphi 11 Version 28.44500.8973 and Windows 10 version 22H2 OS build 19045.3570 64-bit)

To get the error, drop a TClientDataset on a form, right-click the icon and chose ‘Load from MyBase table’. The file to choose is an xml file using the above text.

Regards
Graeme

2

Seems as though some of my xml is missing.

I have attached it below
ADUG CDS.LoadFromStream problem.zip (579 Bytes)

3

When posting code or markup, you need to tell discourse what it is, to do that add a line with 3 backtics and then the language (for highlighting) and the end it with 3 backticks on a separate line

```xml
code/xml goes here
```

I formatted it for easier reading (original had no line breaks).

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<DATAPACKET Version="2.0">
	<METADATA>
		<FIELDS>
			<FIELD attrname="QueueIDs" fieldtype="nested">
				<FIELDS>
					<FIELD attrname="QueueID" fieldtype="i8"/>
					<FIELD attrname="LINK_FIELD" fieldtype="ui4" hidden="true" linkfield="true"/>
				</FIELDS>
				<PARAMS CHANGE_LOG="1 0 4"/>
			</FIELD>
			<FIELD attrname="BillingRunID" fieldtype="i8"/>
			<FIELD attrname="FromDateTime" fieldtype="dateTime"/>
			<FIELD attrname="ToDateTime" fieldtype="dateTime"/>
			<FIELD attrname="ClientIDs" fieldtype="nested">
				<FIELDS>
					<FIELD attrname="ClientID" fieldtype="i8"/>
					<FIELD attrname="Successfull" fieldtype="boolean"/>
					<FIELD attrname="ResultInfo" fieldtype="bin.hex" SUBTYPE="Text"/>
					<FIELD attrname="LINK_FIELD" fieldtype="ui4" hidden="true" linkfield="true"/>
				</FIELDS>
				<PARAMS CHANGE_LOG="1 0 4"/>
			</FIELD>
		</FIELDS>
		<PARAMS CHANGE_LOG="1 0 4 1 2 64 1 1 64"/>
	</METADATA>
	<ROWDATA>
		<ROW RowState="4">
			<QueueIDs>
				<ROWQueueIDs RowState="4" QueueID="1" LINK_FIELD="1"/>
			</QueueIDs> BillingRunID="21798" FromDateTime="20230831" ToDateTime="20231111T23:59:59999"
			<ClientIDs>
				<ROWClientIDs RowState="4" ClientID="21555" LINK_FIELD="1"/>
			</ClientIDs>
		</ROW>
	</ROWDATA>
</DATAPACKET>
4

Thanks Vincent

I will try and remember your instructions for next time.

With respect to my problem it appears that the TClientDataset that has
nested datasets can use the SaveToFile/SaveToStream methods but cannot
load the resultant data using the LoadFromFile/LoadFromStream methods.

I am assuming that in order to use nested datasets a secondary
ClientDataset is required to store/use the nested dataset data.

In my case there is nested data but not CDS to store the data. Hence the
AV on address zero.

Regards
Graeme

5

Does XML Mapper help with this? I seem to remember doing something with nested xml data in the past.

https://docwiki.embarcadero.com/RADStudio/Sydney/en/Using_XMLMapper