无法将类型'System.Version'隐式转换为'System.Net.HttpVersion'

Question

Consider the following code:

void Main()
{
    HttpVersion version;
    string s = "HTTP/1.1";
    version = s == "HTTP/1.1" ? HttpVersion.Version11 : HttpVersion.Version10;
}

This throws the error

Cannot implicitly convert type 'System.Version' to 'System.Net.HttpVersion'

even though System.Version is nowhere inferred and isn't even part of HttpVersion 's inheritance .

Explicit casts

void Main()
{
    HttpVersion version;
    string s = "HTTP/1.1";
    version = s == "HTTP/1.1" ? (HttpVersion) HttpVersion.Version11 : (HttpVersion) HttpVersion.Version10;
}

or explicit namespace naming

void Main()
{
    System.Net.HttpVersion version;
    string s = "HTTP/1.1";
    version = s == "HTTP/1.1" ? System.Net.HttpVersion.Version11 : System.Net.HttpVersion.Version10;
}

don't make a difference.

The question is simple: why is System.Version interfering with what should be an unrelated class?

Answer 1

The Version10 and Version11 static fields of HttpVersion return System.Version objects, not HttpVersion objects. So it's not technically unrelated.

Now as for WHY it does that, I have absolutely no idea. But you'll note that the places where it is used (such as HttpWebRequest.ProtocolVersion ) use System.Version as well. So that's what you want to be using.

To me, it kind of looks kind of like HttpVersion should have been a static class as it has no instance members that are not inherited from Object ...

Answer 2

HttpVersion.Version11和HttpVersion.Version10都返回一个Version对象，您试图将其存储在HttpVersion变量中。