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Asked: 2026-05-28T00:03:29+00:00

I have a simple SOAP apllication: Middle Tier: TSOAPDataModule including TDatasetProvider linked to TADOQuery.

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I have a simple SOAP apllication:
Middle Tier: TSOAPDataModule including TDatasetProvider linked to TADOQuery. TADOQuery has defined a few Parameters (different datatypes)
Client: TClientDataSet linked to TSOAPConnection and provider set to DatasetProvider in MiddleTier.

In design time i can succesfully Fetch Params and Fields for the ClientDataSet from Server. In runtime I programaticaly set parameters for the ClientDataSet and call Open. But I get an SQL error (comming from SQL Server, through ADOQuery in Middle Tier, passed by SOAP to the client) about incorrect values in parameters. After detail debugging I found that the parameters are correctly passed from client to the SOAP server. The Provider.Params lists all the parameters correctly. Unfortunatelly before the ADOQuery opens (after the ADOQuery.Parameters are assigned from the DataSetProvider) the DataType of all the parameters are changed. ie.: original ADOQuery Parameter DataType was ftDateTime but after assignment from DataSetProvider it becomes ftWideString.

This happens for any Parameter DataType that is not null from the Client – all of them become ftWideString.

I have found that this change happens in TParam.Assign where TParameter(Destination).Value is assigned before TParameter(Destination).DataType. After the Value is assigned the DataType is automatically guessed from the varType of the Value. As the Value comes from OleVariant it is always considered to be String.

I tried to alter the TParam.Assign procedure = Assign DataType before Value. But in this way I get ADO Error of Value type being incompatible with DataType.

I think that the problem is in the way tha parameters are being encoded into SOAP XML request. Their values are simply ‘{value}’ without any type information.

I’ve googled a lot for this problem, but didn’t find even a note of simmillar behaviour.

Do I do something wrong, or is this a bug in SOAP in Delphi?

PS: I run Delphi 2009

EDIT:
I just found a sample SOAP request that has the params marshaled in the following structure:

<NS1:V NS2:VarArrayType="8204">
<V xsi:type="xsd:string">param1</V>
<V xsi:type="xsd:string">Frank</V>
<V xsi:type="xsd:byte">1</V>
<V xsi:type="xsd:byte">1</V>
</NS1:V>

The same in my case looks this way:

<NS1:V NS2:VarArrayType="8204">
<V>param1</V>
<V>Frank</V>
<V>1</V>
<V>1</V>
</NS1:V>

I think this is the root of my troubles but do not know how to make my client to add xsi:type attribuge to the SOAP request.

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1 Answer

  1. Editorial Team

    I found it. I have registered my SOAPDataModule with

    InvRegistry.RegisterInterface(TypeInfo(IMyIntf), MyNamespace, 'UTF-8');
InvRegistry.RegisterInvokeOptions(TypeInfo(IMyIntf), [ioDocument, ioHasNamespace, ioIsAppServerSOAP]);

    Including ioDocument in RegisterInvokeOptions made the xsi:type attribute not to be included in Variant type data. This made unmarshaling the param values to olestring types. So the solution for my problem is:

    InvRegistry.RegisterInvokeOptions(TypeInfo(IMyIntf), [ioHasNamespace, ioIsAppServerSOAP]);
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