C# How can I check if a URL exists/is valid?

Question

I am making a simple program in visual c# 2005 that looks up a stock symbol on Yahoo! Finance, downloads the historical data, and then plots the price history for the specified ticker symbol.

I know the exact URL that I need to acquire the data, and if the user inputs an existing ticker symbol (or at least one with data on Yahoo! Finance) it works perfectly fine. However, I have a run-time error if the user makes up a ticker symbol, as the program tries to pull data from a non-existent web page.

I am using the WebClient class, and using the DownloadString function. I looked through all the other member functions of the WebClient class, but didn't see anything I could use to test a URL.

How can I do this?

Answer 1

Here is another implementation of this solution:

using System.Net;

///
/// Checks the file exists or not.
///
/// The URL of the remote file.
/// True : If the file exits, False if file not exists
private bool RemoteFileExists(string url)
{
    try
    {
        //Creating the HttpWebRequest
        HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
        //Setting the Request method HEAD, you can also use GET too.
        request.Method = "HEAD";
        //Getting the Web Response.
        HttpWebResponse response = request.GetResponse() as HttpWebResponse;
        //Returns TRUE if the Status code == 200
        response.Close();
        return (response.StatusCode == HttpStatusCode.OK);
    }
    catch
    {
        //Any exception will returns false.
        return false;
    }
}

From: http://www.dotnetthoughts.net/2009/10/14/how-to-check-remote-file-exists-using-c/