VB -> C#: The LINQ-to-XML attribute axis accessor should be translated as a call to XElement.Attribute rather than XElement.Attributes.

首先重现 issue 中的 VB.NET 输入，并检查 LINQ-to-XML 属性轴转换的入口点。将生成的 Attributes 调用与预期的 Attribute 调用和 string 强制转换进行比较。完成的标准是，现有属性和缺失属性都生成预期的 C# 表达式，并保留所示的运行时行为。

VB.Net input code

    Dim x = <MyTag MyAttribute="a"/>

    Dim existingAttributeValue As String = x.@MyAttribute
    Dim missingAttributeValue As String = x.@MissingAttribute

    Console.WriteLine(existingAttributeValue = "a")
    Console.WriteLine(missingAttributeValue Is Nothing)

Erroneous output

(snipped to the relevant part)

    string existingAttributeValue = x.Attributes("MyAttribute");
    string missingAttributeValue = x.Attributes("MissingAttribute");

Expected output

    string existingAttributeValue = (string)x.Attribute("MyAttribute");
    string missingAttributeValue = (string)x.Attribute("MissingAttribute");

Details

• Product in use: icsharpcode.github.io/CodeConverter [NB: Here's a typo in the github issue template] / VS extension 9.0.4.0
• VB.NET's x.@AttributeName returns a string, and so should the converted C# expression. Casting the result to string (using the explicit conversion defined in XAttribute) seems to be the idiomatic way in C# to get this value. In addition, that's also what the VB compiler does (indirectly, via a call to My.InternalXmlHelper). Multiple matching attributes (which would be an argument for calling Attributes) are not an issue, since attribute names must be unique within an XElement, and the documentation of XElement.Attributes(XName) explicitly states that the returned collection always contains exactly 0 or 1 elements.