LINQ to XML aggregates and group by

I'm Attemping to do a SUM and a Group By in LINQ to XML. I'm also using LINQPad 4 to test my linq out. For some reason rate = g.Sum(taxRate) is giving me a FormatException error. I'm pretty sure this LINQ query could be cleared up as well. I know that "Taxrate" can be an empty string, I wish to just default 0 or ignore any empties. Any suggestions?

var tax = from taxRate in TaxRates.Descendants("Code")
          where 
          taxRate.Attribute("taxrate") != null 
          &&
          Int32.Parse(taxRate.Attribute("taxyear").Value) == TaxYear
          group taxRate by taxRate.Attribute("taxunitid").Value into g
          select new
          {
              ID = g.Key,
              rate = g.Sum(taxRate => Decimal.Parse(taxRate.Attribute("taxrate").Value))
          };
taxRatesByTaxUnit.Dump();

Here's some sample xml.

<Code taxyear="2005" tusfundid="12" cycleid="575" taxunitid="198674" taxrate=".214000000"/>
<Code taxyear="2005" tusfundid="13" cycleid="575" taxunitid="198674" taxrate=".004"/>
<Code taxyear="2005" tusfundid="13" cycleid="575" taxunitid="198674" taxrate=""/>
<Code taxyear="2005" tusfundid="13" cycleid="575" taxunitid="100000" taxrate=""/>

I expect to get back of 

taxunit id: 198674: taxrate = .218  
taxunit id: 100000: taxrate = .000
Jon Skeet
people
quotationmark

Okay, given the "tax rate of an empty string should be treated as 0", I would probably break that up into a separate method. It's simpler than trying to do it inline. Then I'd use explicit conversions everywhere.

So something like:

private decimal GetTaxRate(XElement code)
{
    XAttribute rateAttribute = code.Attribute("taxRate");
    return (string) rateAttribute == "" ? 0m : (decimal) rateAttribute;
}

...

var query = from code in TaxRates.Descendants("Code")
            where (int?) code.Attribute("taxyear") == TaxYear
               && code.Attribute("taxRate") != null
            group code by (string) code.Attribute("taxunitid") into g
            select new {
                ID = g.Key,
                rate = g.Sum(code => GetTaxRate(code))
            };
query.Dump();

people

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