LINQ to XML Sum Child Nodes in VB.NET

问题

I have the following XML from Amazon's Marketplace API. I need to sum all the values of Item/ItemPrice/Component[type='Principal']/Amount for all Items to compute an order total. Is this possible to do using LINQ to XML in VB.NET?

<?xml version="1.0"?>
<AmazonEnvelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="amzn-envelope.xsd">
  <Header>
    <DocumentVersion>1.01</DocumentVersion>
    <MerchantIdentifier>My Store</MerchantIdentifier>
  </Header>
  <MessageType>OrderReport</MessageType>
  <Message>
    <MessageID>1</MessageID>
    <OrderReport>
      <AmazonOrderID>050-1234567-1234567</AmazonOrderID>
      <AmazonSessionID>902-1030835-1234567</AmazonSessionID>
      <OrderDate>2002-05-01T15:20:15-08:00</OrderDate>
      <OrderPostedDate>2002-05-01T15:21:49-08:00</OrderPostedDate>
      <BillingData>
        <BuyerEmailAddress>joesmith@hotmail.com</BuyerEmailAddress>
        <BuyerName>Joe Smith</BuyerName>
        <BuyerPhoneNumber>206-555-1234</BuyerPhoneNumber>
      </BillingData>
      <FulfillmentData>
        <FulfillmentMethod>Ship</FulfillmentMethod>
        <FulfillmentServiceLevel>Standard</FulfillmentServiceLevel>
        <Address>
          <Name>Joe Smith</Name>
          <AddressFieldOne>1234 Main St.</AddressFieldOne>
          <City>Seattle</City>
          <StateOrRegion>Washington</StateOrRegion>
          <PostalCode>98004</PostalCode>
          <CountryCode>US</CountryCode>
          <PhoneNumber>206-555-1234</PhoneNumber>
        </Address>
      </FulfillmentData>
      <Item>
        <AmazonOrderItemCode>12345678901234</AmazonOrderItemCode>
        <SKU>1234</SKU>
        <Title>Programming Perl, 3rd edition</Title>
        <Quantity>1</Quantity>
        <ProductTaxCode>1234</ProductTaxCode>
        <ItemPrice>
          <Component>
            <Type>Principal</Type>
            <Amount currency="USD">10.00</Amount>
          </Component>
          <Component>
            <Type>Shipping</Type>
            <Amount currency="USD">3.49</Amount>
          </Component>
          <Component>
            <Type>Tax</Type>
            <Amount currency="USD">1.29</Amount>
          </Component>
          <Component>
            <Type>ShippingTax</Type>
            <Amount currency="USD">0.24</Amount>
          </Component>
        </ItemPrice>
        <ItemFees>
          <Fee>
            <Type>Commission</Type>
            <Amount currency="USD">-0.75</Amount>
          </Fee>
        </ItemFees>
        <ItemTaxData>
          <TaxJurisdictions>
            <TaxLocationCode>12345678</TaxLocationCode>
            <City>Seattle</City>
            <County>King</County>
            <State>WA</State>
          </TaxJurisdictions>
          <TaxableAmounts>
            <District currency="USD">10.00</District>
            <City currency="USD">10.00</City>
            <County currency="USD">0.00</County>
            <State currency="USD">10.00</State>
          </TaxableAmounts>
          <NonTaxableAmounts>
            <District currency="USD">0.00</District>
            <City currency="USD">0.00</City>
            <County currency="USD">10.00</County>
            <State currency="USD">0.00</State>
          </NonTaxableAmounts>
          <ZeroRatedAmounts>
            <District currency="USD">0.00</District>
            <City currency="USD">0.00</City>
            <County currency="USD">0.00</County>
            <State currency="USD">0.00</State>
          </ZeroRatedAmounts>
          <TaxCollectedAmounts>
            <District currency="USD">0.23</District>
            <City currency="USD">0.53</City>
            <County currency="USD">0.00</County>
            <State currency="USD">0.53</State>
          </TaxCollectedAmounts>
          <TaxRates>
            <District>0.0230</District>
            <City>0.0530</City>
            <County>0.0230</County>
            <State>0.0530</State>
          </TaxRates>
        </ItemTaxData>
        <ShippingTaxData>
          <TaxJurisdictions>
            <TaxLocationCode>12345678</TaxLocationCode>
            <City>Seattle</City>
            <County>King</County>
            <State>WA</State>
          </TaxJurisdictions>
          <TaxableAmounts>
            <District currency="USD">3.49</District>
            <City currency="USD">3.49</City>
            <County currency="USD">0.00</County>
            <State currency="USD">3.49</State>
          </TaxableAmounts>
          <NonTaxableAmounts>
            <District currency="USD">0.00</District>
            <City currency="USD">0.00</City>
            <County currency="USD">3.49</County>
            <State currency="USD">0.00</State>
          </NonTaxableAmounts>
          <ZeroRatedAmounts>
            <District currency="USD">0.00</District>
            <City currency="USD">0.00</City>
            <County currency="USD">0.00</County>
            <State currency="USD">0.00</State>
          </ZeroRatedAmounts>
          <TaxCollectedAmounts>
            <District currency="USD">0.04</District>
            <City currency="USD">0.10</City>
            <County currency="USD">0.00</County>
            <State currency="USD">0.10</State>
          </TaxCollectedAmounts>
          <TaxRates>
            <District>0.0120</District>
            <City>0.0190</City>
            <County>0.0190</County>
            <State>0.0190</State>
          </TaxRates>
        </ShippingTaxData>
        <Promotion>
          <PromotionClaimCode>ABC123</PromotionClaimCode>
          <MerchantPromotionID>12345678</MerchantPromotionID>
          <Component>
            <Type>Principal</Type>
            <Amount currency="USD">-1.00</Amount>
          </Component>
        </Promotion>
      </Item>
      <Item>
        <AmazonOrderItemCode>12345678901235</AmazonOrderItemCode>
        <SKU>1234</SKU>
        <Title>Programming ASP.NET, 2nd edition</Title>
        <Quantity>1</Quantity>
        <ProductTaxCode>1234</ProductTaxCode>
        <ItemPrice>
          <Component>
            <Type>Principal</Type>
            <Amount currency="USD">12.00</Amount>
          </Component>
          <Component>
            <Type>Shipping</Type>
            <Amount currency="USD">3.49</Amount>
          </Component>
          <Component>
            <Type>Tax</Type>
            <Amount currency="USD">1.42</Amount>
          </Component>
          <Component>
            <Type>ShippingTax</Type>
            <Amount currency="USD">0.24</Amount>
          </Component>
        </ItemPrice>
        <ItemFees>
          <Fee>
            <Type>Commission</Type>
            <Amount currency="USD">-0.75</Amount>
          </Fee>
        </ItemFees>
        <ItemTaxData>
          <TaxJurisdictions>
            <TaxLocationCode>12345678</TaxLocationCode>
            <City>Seattle</City>
            <County>King</County>
            <State>WA</State>
          </TaxJurisdictions>
          <TaxableAmounts>
            <District currency="USD">10.00</District>
            <City currency="USD">10.00</City>
            <County currency="USD">0.00</County>
            <State currency="USD">10.00</State>
          </TaxableAmounts>
          <NonTaxableAmounts>
            <District currency="USD">0.00</District>
            <City currency="USD">0.00</City>
            <County currency="USD">10.00</County>
            <State currency="USD">0.00</State>
          </NonTaxableAmounts>
          <ZeroRatedAmounts>
            <District currency="USD">0.00</District>
            <City currency="USD">0.00</City>
            <County currency="USD">0.00</County>
            <State currency="USD">0.00</State>
          </ZeroRatedAmounts>
          <TaxCollectedAmounts>
            <District currency="USD">0.23</District>
            <City currency="USD">0.53</City>
            <County currency="USD">0.00</County>
            <State currency="USD">0.53</State>
          </TaxCollectedAmounts>
          <TaxRates>
            <District>0.0230</District>
            <City>0.0530</City>
            <County>0.0230</County>
            <State>0.0530</State>
          </TaxRates>
        </ItemTaxData>
        <ShippingTaxData>
          <TaxJurisdictions>
            <TaxLocationCode>12345678</TaxLocationCode>
            <City>Seattle</City>
            <County>King</County>
            <State>WA</State>
          </TaxJurisdictions>
          <TaxableAmounts>
            <District currency="USD">3.49</District>
            <City currency="USD">3.49</City>
            <County currency="USD">0.00</County>
            <State currency="USD">3.49</State>
          </TaxableAmounts>
          <NonTaxableAmounts>
            <District currency="USD">0.00</District>
            <City currency="USD">0.00</City>
            <County currency="USD">3.49</County>
            <State currency="USD">0.00</State>
          </NonTaxableAmounts>
          <ZeroRatedAmounts>
            <District currency="USD">0.00</District>
            <City currency="USD">0.00</City>
            <County currency="USD">0.00</County>
            <State currency="USD">0.00</State>
          </ZeroRatedAmounts>
          <TaxCollectedAmounts>
            <District currency="USD">0.04</District>
            <City currency="USD">0.10</City>
            <County currency="USD">0.00</County>
            <State currency="USD">0.10</State>
          </TaxCollectedAmounts>
          <TaxRates>
            <District>0.0120</District>
            <City>0.0190</City>
            <County>0.0190</County>
            <State>0.0190</State>
          </TaxRates>
        </ShippingTaxData>
        <Promotion>
          <PromotionClaimCode>ABC123</PromotionClaimCode>
          <MerchantPromotionID>12345678</MerchantPromotionID>
          <Component>
            <Type>Principal</Type>
            <Amount currency="USD">-1.00</Amount>
          </Component>
        </Promotion>
      </Item>
    </OrderReport>
  </Message>
</AmazonEnvelope>

回答1:

This is how you'd solve this in VB using the more idomatic inline-XML with Linq syntax.

Dim result =
   From xcmp In azm...<Item>.<ItemPrice>.<Component>
   Where xcmp.<Type>.Value = "Principal"
   Select Convert.ToDecimal(xcmp.<Amount>.Value)

Console.WriteLine(result.Sum().ToString())

The triple dot syntax is for descendant searches. The single dot syntax moves to the child node. The azm variable is an XDocument holding your XML.

回答2:

Here's the c# version that would work

XDocument d = XDocument.Load(xmlFileName);
var sum = d.Root.Descendants("Item").Where(i => i.Element("ItemPrice")
                                                 .Element("Component")
                                                 .Element("Type")
                                                 .Value == "Principal")
                                    .Sum(i => Convert.ToDouble(i.Element("ItemPrice")
                                                               .Element("Component")
                                                               .Element("Amount")
                                                               .Value));

See if you can use a converter such as http://converter.telerik.com/ to convert to vb.net to use it.

Here's what I got from automatic conversion.

Dim d As XDocument = XDocument.Load(xmlFileName)
Dim sum = d.Root.Descendants("Item").Where(Function(i) i.Element("ItemPrice").Element("Component").Element("Type").Value = "Principal").Sum(Function(i) Convert.ToDouble(i.Element("ItemPrice").Element("Component").Element("Amount").Value))

EDIT:

Switched from Convert.ToInt64() to Convert.ToDouble().

回答3:

Try this code

    Dim foo As List(Of Decimal) = (From i In xmlstring.Descendants("Component")
                                   Where i.Parent.Name = "ItemPrice"
                                   Where i.Element("Type") = "Principal"
                                   Select Convert.ToDecimal(i.Element("Amount").Value)).ToList()

    Dim result = foo.Sum()

xmlstring variable is the xdocument.

回答4:

I need to sum all the values of Item/ItemPrice/Component[type='Principal']/Amount for all Items to compute an order total.

This XPath expression:

sum(
  /AmazonEnvelope
    /Message
      /OrderReport
        /Item
          /ItemPrice
            /Component[Type='Principal']
              /Amount
)

Result: 22

来源：https://stackoverflow.com/questions/5875015/linq-to-xml-sum-child-nodes-in-vb-net

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