System.Net.Uri with urlencoded characters

Question

I need to request the following URL inside my application:

http://feedbooks.com/type/Crime%2FMystery/books/top

When I run the following code:

Uri myUri = new Uri("http://feedbooks.com/type/Crime%2FMystery/books/top");

The Uri constructor decodes the %2F into a literal /, and I get a 404 error because it has changed the URL to:

http://feedbooks.com/type/Crime/Mystery/books/top

The Uri class has a constructor that takes a parameter dontEscape, but that constructor is deprecated and setting it to true has no effect.

My first thought was to do something like:

Uri myUri = new Uri("http://feedbooks.com/type/Crime%252FMystery/books/top");

With the hopes that it would convert %25 into a literal %, but that didn't work either.

Any ideas how to create a correct Uri object for this particular URL in .NET?

Answer 1

It's a bit easier in .NET 4.0. You can put a setting in your config file like this:

<uri> 
<schemeSettings>
 <add name="http" genericUriParserOptions="DontUnescapePathDotsAndSlashes" />
</schemeSettings>
</uri>

It only works for the 'http' and 'https' schemes.

Or here's a new version of the LeaveDotsAndSlashesEscaped method. It doesn't need a particular Uri instance, just call it when your application starts up:

private void LeaveDotsAndSlashesEscaped()
{
 var getSyntaxMethod = 
 typeof (UriParser).GetMethod("GetSyntax", BindingFlags.Static | BindingFlags.NonPublic);
 if (getSyntaxMethod == null)
 {
 throw new MissingMethodException("UriParser", "GetSyntax");
 }
 var uriParser = getSyntaxMethod.Invoke(null, new object[] { "http" });
 var setUpdatableFlagsMethod = 
 uriParser.GetType().GetMethod("SetUpdatableFlags", BindingFlags.Instance | BindingFlags.NonPublic);
 if (setUpdatableFlagsMethod == null)
 {
 throw new MissingMethodException("UriParser", "SetUpdatableFlags");
 }
 setUpdatableFlagsMethod.Invoke(uriParser, new object[] {0});
}

Answer 2

I ran into the same problem using 2.0...

I discovered a workaround posted at this blog:

// System.UriSyntaxFlags is internal, so let's duplicate the flag privately
private const int UnEscapeDotsAndSlashes = 0x2000000;
public static void LeaveDotsAndSlashesEscaped(Uri uri)
{
 if (uri == null)
 {
 throw new ArgumentNullException("uri");
 }
 FieldInfo fieldInfo = uri.GetType().GetField("m_Syntax", BindingFlags.Instance | BindingFlags.NonPublic);
 if (fieldInfo == null)
 {
 throw new MissingFieldException("'m_Syntax' field not found");
 }
 object uriParser = fieldInfo.GetValue(uri);
 fieldInfo = typeof(UriParser).GetField("m_Flags", BindingFlags.Instance | BindingFlags.NonPublic);
 if (fieldInfo == null)
 {
 throw new MissingFieldException("'m_Flags' field not found");
 }
 object uriSyntaxFlags = fieldInfo.GetValue(uriParser);
 // Clear the flag that we don't want
 uriSyntaxFlags = (int)uriSyntaxFlags & ~UnEscapeDotsAndSlashes;
 fieldInfo.SetValue(uriParser, uriSyntaxFlags);
}

It works perfectly.

Hope this helps (better late than never!)

Answer 3

This is a bug I filed a while back. It's supposed to be fixed in 4.0, but I'm not holding my breath. Apparently it's still a problem in the RC.

Answer 4

By combining the 2 previous answers you can have a method you only need to call once per process that works both on .net 4 and .net 3.5.

// System.UriSyntaxFlags is internal, so let's duplicate the flag privately
private const int UnEscapeDotsAndSlashes = 0x2000000;
private void LeaveDotsAndSlashesEscaped()
{
 var getSyntaxMethod = 
 typeof (UriParser).GetMethod("GetSyntax", BindingFlags.Static | BindingFlags.NonPublic);
 if (getSyntaxMethod == null)
 {
 throw new MissingMethodException("UriParser", "GetSyntax");
 }
 var uriParser = getSyntaxMethod.Invoke(null, new object[] { "http" });
 FieldInfo flagsFieldInfo = typeof(UriParser).GetField("m_Flags", BindingFlags.NonPublic | BindingFlags.GetField | BindingFlags.SetField | BindingFlags.Instance);
 if (flagsFieldInfo == null)
 {
 throw new MissingFieldException("UriParser", "m_Flags");
 }
 int flags = (int) flagsFieldInfo.GetValue(uriParser);
 // unset UnEscapeDotsAndSlashes flag and leave the others untouched
 flags = flags & ~UnEscapeDotsAndSlashes;
 flagsFieldInfo.SetValue(uriParser, flags);
}