To override the Content-type in your clients, use the HTTP Accept Header, append  the .xml suffix or  ?format=xml
        
        HTTP + XML
         The following are sample HTTP requests and responses. 
            The placeholders shown need to be replaced with actual values.
GET /coupons HTTP/1.1 
Host: blazor-gallery.servicestack.net 
Accept: application/xml
 
HTTP/1.1 200 OK
Content-Type: application/xml
Content-Length: length
<QueryResponseOfCoupontlJ4_P31p xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.servicestack.net/types">
  <Offset>0</Offset>
  <Total>0</Total>
  <Results xmlns:d2p1="http://schemas.datacontract.org/2004/07/MyApp.ServiceModel">
    <d2p1:Coupon>
      <d2p1:Description>String</d2p1:Description>
      <d2p1:Discount>0</d2p1:Discount>
      <d2p1:ExpiryDate>0001-01-01T00:00:00</d2p1:ExpiryDate>
      <d2p1:Id>String</d2p1:Id>
    </d2p1:Coupon>
  </Results>
  <Meta xmlns:d2p1="http://schemas.microsoft.com/2003/10/Serialization/Arrays">
    <d2p1:KeyValueOfstringstring>
      <d2p1:Key>String</d2p1:Key>
      <d2p1:Value>String</d2p1:Value>
    </d2p1:KeyValueOfstringstring>
  </Meta>
  <ResponseStatus>
    <ErrorCode>String</ErrorCode>
    <Message>String</Message>
    <StackTrace>String</StackTrace>
    <Errors>
      <ResponseError>
        <ErrorCode>String</ErrorCode>
        <FieldName>String</FieldName>
        <Message>String</Message>
        <Meta xmlns:d5p1="http://schemas.microsoft.com/2003/10/Serialization/Arrays">
          <d5p1:KeyValueOfstringstring>
            <d5p1:Key>String</d5p1:Key>
            <d5p1:Value>String</d5p1:Value>
          </d5p1:KeyValueOfstringstring>
        </Meta>
      </ResponseError>
    </Errors>
    <Meta xmlns:d3p1="http://schemas.microsoft.com/2003/10/Serialization/Arrays">
      <d3p1:KeyValueOfstringstring>
        <d3p1:Key>String</d3p1:Key>
        <d3p1:Value>String</d3p1:Value>
      </d3p1:KeyValueOfstringstring>
    </Meta>
  </ResponseStatus>
</QueryResponseOfCoupontlJ4_P31p>