Add scheme to URL if needed

c# .net uri
Max Favilli picture Max Favilli · Mar 13, 2011 · Viewed 28.6k times · Source

To create a Uri from a string you can do this:

Uri u = new Uri("example.com");

But the problem is if the string (like the one above) doesn't contain the protocol you will get an exception: "Invalid URI: The format of the URI could not be determined."

To avoid the exception you should secure the string includes a protocol, like below:

Uri u = new Uri("http://example.com");

But if you take the url as input, how can you add the protocol if it's missing?
I mean apart from some IndexOf/Substring manipulation?

Something elegant and fast?

Answer

as-cii picture as-cii · Mar 13, 2011

You could also use UriBuilder:

public static Uri GetUri(this string s)
{
    return new UriBuilder(s).Uri;
}

Remarks from MSDN:

This constructor initializes a new instance of the UriBuilder class with the Fragment, Host, Path, Port, Query, Scheme, and Uri properties set as specified in uri.

If uri does not specify a scheme, the scheme defaults to "http:".

Related questions

Invalid URI: The format of the URI could not be determined

I keep getting this error. Invalid URI: The format of the URI could not be determined. the code I have is: Uri uri = new Uri(slct.Text); if (DeleteFileOnServer(uri)) { nn.BalloonTipText = slct.Text + " has been deleted."; nn.ShowBalloonTip(30); } Update: …

Read More
Convert file path to a file URI?

Does the .NET Framework have any methods for converting a path (e.g. "C:\whatever.txt") into a file URI (e.g. "file:///C:/whatever.txt")? The System.Uri class has the reverse (from a file URI to absolute path), …

Read More
How to check whether a string is a valid HTTP URL?

There are the Uri.IsWellFormedUriString and Uri.TryCreate methods, but they seem to return true for file paths etc. How do I check whether a string is a valid (not necessarily active) HTTP URL for input validation purposes?

Read More