问题
I have an xml and it has nodes with i:nil="true" in it. What does that mean?
For example:
<FirstName i:nil="true" />
Does that mean something different than:
<FirstName />
If so, what is the difference?
回答1:
This means FirstName is null
<FirstName i:nil="true" />
This means FirstName = ""
<FirstName />
Assumption made on FirstName is of string type.
回答2:
Maybe i:nil actually means xsi:nil, this means that the FirstName element is empty, i.e. does not have any content -- not even "". It refers to the nillable property in XML Schema.
回答3:
nil is an attribute, defined in the i namespace. For this FirstName node, the attribute has the value true.
It's similar to this, just with different names and values:
<form name="test">...
Here, form is the name of the node, similar to FirstName from your code, and name is an attribute with a value of "test", similar to your attribute nil with a value of "true".
What this means depends on the application reading the xml document.
If I were to venture a guess, I'd say that this looks like part of a xml document defining some kind of schema, and that the FirstName field can have a NULL or nil value, meaning empty, or unknown.
来源：https://stackoverflow.com/questions/463597/what-does-inil-true-mean