Linq-to-XML explicit casting in a generic method
- by vlad
I've looked for a similar question, but the only one that was close didn't help me in the end.
I have an XML file that looks like this:
<Fields>
<Field name="abc" value="2011-01-01" />
<Field name="xyz" value="" />
<Field name="tuv" value="123.456" />
</Fields>
I'm trying to use Linq-to-XML to get the values from these fields. The values can be of type Decimal, DateTime, String and Int32. I was able to get the fields one by one using a relatively simple query. For example, I'm getting the 'value' from the field with the name 'abc' using the following:
private DateTime GetValueFromAttribute(IEnumerable<XElement> fields, String attName)
{
return (from field in fields
where field.Attribute("name").Value == "abc"
select (DateTime)field.Attribute("value")).FirstOrDefault()
}
this is placed in a separate function that simply returns this value, and everything works fine (since I know that there is only one element with the name attribute set to 'abc'). however, since I have to do this for decimals and integers and dates, I was wondering if I can make a generic function that works in all cases. this is where I got stuck. here's what I have so far:
private T GetValueFromAttribute<T>(IEnumerable<XElement> fields, String attName)
{
return (from field in fields
where field.Attribute("name").Value == attName
select (T)field.Attribute("value").Value).FirstOrDefault();
}
this doesn't compile because it doesn't know how to convert from String to T. I tried boxing and unboxing (i.e. select (T) (Object) field.Attribute("value").Value but that throws a runtime Specified cast is not valid exception as it's trying to convert the String to a DateTime, for instance.
Is this possible in a generic function? can I put a constraint on the generic function to make it work? or do I have to have separate functions to take advantage of Linq-to-XML's explicit cast operators?
