Question

I am working with existing code and hoping to change data without recompiling _{(as such this could be seen as a SuperUser issue)}.

We currently DataSet.ReadXml from a (compiled) resources-based XML file. Then we check for a local XML file and, if present, DataSet.ReadXml that file and then DataSet.Merge the result into the original.

Seeing as we have no schema in the compiled resources-based XML, there is no way for the external XML to override any data, only add to it, yes?

Answer 1

My question title may have seemed to preclude this option, but it wasn’t intended:

You can get the local file’s data to override the compiled file, by including the xs:schema as the first sub-element of the XML.

I.e. when the original data has no schema, the merged schema will be used.

E.g.

Original:

<NewDataSet>
  <dt1>
    <k>1</k>
    <l>test</l>
    <m>1</m>
  </dt1>
  <dt1>
    <k>2</k>
    <l>test</l>
    <m>2</m>
  </dt1>
  <dt1>
    <k>2</k>
    <l>tst</l>
    <m>3</m>
  </dt1>
</NewDataSet>

New:

<NewDataSet>
 <xs:schema id="NewDataSet" xmlns="" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
  <xs:element name="NewDataSet" msdata:IsDataSet="true" msdata:UseCurrentLocale="true">
    <xs:complexType>
      <xs:choice minOccurs="0" maxOccurs="unbounded">
        <xs:element name="dt1">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="k" type="xs:string" />
              <xs:element name="l" type="xs:string" />
              <xs:element name="m" type="xs:string" minOccurs="0" />
            </xs:sequence>
          </xs:complexType>
        </xs:element>
      </xs:choice>
    </xs:complexType>
    <xs:unique name="Constraint1" msdata:PrimaryKey="true">
      <xs:selector xpath=".//dt1" />
      <xs:field xpath="k" />
      <xs:field xpath="l" />
    </xs:unique>
  </xs:element>
 </xs:schema>
  <dt1>
    <k>1</k>
    <l>test</l>
    <m>1</m>
  </dt1>
  <dt1>
    <k>2</k>
    <l>test</l>
    <m>3</m>
  </dt1>
  <dt1>
    <k>3</k>
    <l>test</l>
    <m>4</m>
  </dt1>
</NewDataSet>

Merged (for simplicity I include the WriteXml output):

<NewDataSet>
  <dt1>
    <k>1</k>
    <l>test</l>
    <m>1</m>
  </dt1>
  <dt1>
    <k>2</k>
    <l>test</l>
    <m>3</m>
  </dt1>
  <dt1>
    <k>2</k>
    <l>tst</l>
    <m>3</m>
  </dt1>
  <dt1>
    <k>3</k>
    <l>test</l>
    <m>4</m>
  </dt1>
</NewDataSet>