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.
POST /cached/customers/{Id} HTTP/1.1 
Host: northwind.netcore.io 
Accept: application/xml
Content-Type: application/xml
Content-Length: length
<CachedGetCustomerDetails xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.datacontract.org/2004/07/Northwind.ServiceModel">
  <Id>String</Id>
</CachedGetCustomerDetails>
 
HTTP/1.1 200 OK
Content-Type: application/xml
Content-Length: length
<CustomerDetailsResponse xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.datacontract.org/2004/07/Northwind.ServiceModel">
  <Customer xmlns:d2p1="http://schemas.datacontract.org/2004/07/Northwind.ServiceModel.Types">
    <d2p1:Address>String</d2p1:Address>
    <d2p1:City>String</d2p1:City>
    <d2p1:CompanyName>String</d2p1:CompanyName>
    <d2p1:ContactName>String</d2p1:ContactName>
    <d2p1:ContactTitle>String</d2p1:ContactTitle>
    <d2p1:Country>String</d2p1:Country>
    <d2p1:Fax>String</d2p1:Fax>
    <d2p1:Id>String</d2p1:Id>
    <d2p1:Phone>String</d2p1:Phone>
    <d2p1:PostalCode>String</d2p1:PostalCode>
    <d2p1:Region>String</d2p1:Region>
  </Customer>
  <Orders xmlns:d2p1="http://schemas.datacontract.org/2004/07/Northwind.ServiceModel.Types">
    <d2p1:CustomerOrder>
      <d2p1:Order>
        <d2p1:CustomerId>String</d2p1:CustomerId>
        <d2p1:EmployeeId>0</d2p1:EmployeeId>
        <d2p1:Freight>0</d2p1:Freight>
        <d2p1:Id>0</d2p1:Id>
        <d2p1:OrderDate>0001-01-01T00:00:00</d2p1:OrderDate>
        <d2p1:RequiredDate>0001-01-01T00:00:00</d2p1:RequiredDate>
        <d2p1:ShipAddress>String</d2p1:ShipAddress>
        <d2p1:ShipCity>String</d2p1:ShipCity>
        <d2p1:ShipCountry>String</d2p1:ShipCountry>
        <d2p1:ShipName>String</d2p1:ShipName>
        <d2p1:ShipPostalCode>String</d2p1:ShipPostalCode>
        <d2p1:ShipRegion>String</d2p1:ShipRegion>
        <d2p1:ShipVia>0</d2p1:ShipVia>
        <d2p1:ShippedDate>0001-01-01T00:00:00</d2p1:ShippedDate>
      </d2p1:Order>
      <d2p1:OrderDetails>
        <d2p1:OrderDetail>
          <d2p1:Discount>0</d2p1:Discount>
          <d2p1:OrderId>0</d2p1:OrderId>
          <d2p1:ProductId>0</d2p1:ProductId>
          <d2p1:Quantity>0</d2p1:Quantity>
          <d2p1:UnitPrice>0</d2p1:UnitPrice>
        </d2p1:OrderDetail>
      </d2p1:OrderDetails>
    </d2p1:CustomerOrder>
  </Orders>
  <ResponseStatus xmlns:d2p1="http://schemas.servicestack.net/types">
    <d2p1:ErrorCode>String</d2p1:ErrorCode>
    <d2p1:Message>String</d2p1:Message>
    <d2p1:StackTrace>String</d2p1:StackTrace>
    <d2p1:Errors>
      <d2p1:ResponseError>
        <d2p1:ErrorCode>String</d2p1:ErrorCode>
        <d2p1:FieldName>String</d2p1:FieldName>
        <d2p1:Message>String</d2p1:Message>
        <d2p1: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>
        </d2p1:Meta>
      </d2p1:ResponseError>
    </d2p1:Errors>
    <d2p1: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>
    </d2p1:Meta>
  </ResponseStatus>
</CustomerDetailsResponse>