What is the best way to check for Internet connectivity using .NET?

Question

What is the fastest and most efficient way to check for Internet connectivity in .NET?

Answer 1

I have three tests for an Internet connection.

• Reference System.Net and System.Net.Sockets
• Add the following test functions:

Test 1

public bool IsOnlineTest1()
{
    try
    {
        IPHostEntry dummy = Dns.GetHostEntry("https://www.google.com");
        return true;
    }
    catch (SocketException ex)
    {
        return false;
    }
}

Test 2

public bool IsOnlineTest2()
{
    try
    {
        IPHostEntry dummy = Dns.GetHostEntry("https://www.google.com");
        return true;
    }
    catch (SocketException ex)
    {
        return false;
    }
}

Test 3

public bool IsOnlineTest3()
{
    System.Net.WebRequest req = System.Net.WebRequest.Create("https://www.google.com");
    System.Net.WebResponse resp = default(System.Net.WebResponse);
    try
    {
        resp = req.GetResponse();
        resp.Close();
        req = null;
        return true;
    }
    catch (Exception ex)
    {
        req = null;
        return false;
    }
}

Performing the tests

If you make a Dictionary of String and Boolean called CheckList, you can add the results of each test to CheckList.

Now, recurse through each KeyValuePair using a for...each loop.

If CheckList contains a Value of true, then you know there is an Internet connection.