在方法中更改Textbox.text; 因为返回而导致循环不循环

Question

Below is a button, when pressed it calls a function that pings a bunch of IP addresses. If the IP address returns a response, it adds the IP address to the output_networkSearch.Text.

private void button_networkSearch_Click(object sender, RoutedEventArgs e)
    {
        output_networkSearch.Text = networkSearch(Convert.ToInt32(input_searchLimit.Text)); 

    }

Below isn't the whole method, just the part that I can't get to work. The for loop starts at whatever the last digit on the users default gateway IP address is, and stops at whatever limit they have inputed (1 - 255).

// i is equal to the last digit in the default gateway IP, if it was 192.168.0.1 then i = 1.

for (int i = Convert.ToInt32(splitGatewayIP[3]); i <= searchLimit; i = i + 1)
                    {
                        // If the method receieves a ping reply...
                        if (PingHostSweep(gatewayIPRebuild + i))
                        {
                            // Returns 192.168.0. + i + ACTIVE
                            string response = gatewayIPRebuild + i + " ACTIVE";

                            return response;
                        }
                        else
                        {
                            string response = gatewayIPRebuild + i + " CLOSED";

                            return response;

                        }
                    }

This worked on a console application but for a WPF application it seems to run through the loop once and stop due to the return statement.

My idea to work around this would be to remove the Return Response statements and try and access the TextBox (output_networkSearch) directly.

So I would do something like:

for (int i = Convert.ToInt32(splitGatewayIP[3]); i <= searchLimit; i = i + 1)
                    {
                        // If the method receieves a ping reply...
                        if (PingHostSweep(gatewayIPRebuild + i))
                        {
                            // Returns 192.168.0. + i + ACTIVE
                            string response = gatewayIPRebuild + i + " ACTIVE";

                            output_networkSearch.Text = reponse;
                        }
                        else
                        {
                            string response = gatewayIPRebuild + i + " CLOSED";

                           output_networkSearch.Text = reponse;

                        }
                    }

HOWEVER, I can't access the textbox within the method for some reason. I've only just started learning C# so I'm not entirely familiar with how it works.

Here's an image of a partially working concept. As you can see the limit is set at 10, so it should ping IP address 1 through 10 and give an ACTIVE or CLOSED response. This did work in my console application version.

WPF version

Console version

Answer 1

This might do the trick for you

List<string> responses = new List<string>();
string response;
for (int i = Convert.ToInt32(splitGatewayIP[3]); i <= searchLimit; i = i + 1)
{
    if (PingHostSweep(gatewayIPRebuild + i))
    {
        response = gatewayIPRebuild + i + " ACTIVE";
    }
    else
    {
        response = gatewayIPRebuild + i + " CLOSED";
    }
    responses.Add(response)
}

Now after the loop the list which is responses would have the list of all the IPs which are active and closed. Like the way you do had in the console Application.

Answer 2

i think you need use threading , there are need many child threading work in backend to scan, when they finish them work then response the result to MainForm, so i write some code hope can help you!

using System.Threading;
using System.Threading.Tasks;


        public void Start(string ip)
        {
            Task.Factory.StartNew(() =>
           {
                // If the method receieves a ping reply...
                string response;
               if (PingHostSweep(ip))
               {
                    // Returns 192.168.0. + i + ACTIVE
                    response = ip + " ACTIVE";
               }
               else
               {
                   response = ip + " CLOSED";
               }
               this.Invoke((MethodInvoker)(() => { textBox1.AppendText("\r\n" + response); }));

           });
        }


        private void button1_Click(object sender, EventArgs e)
        {

            for (int i = 1; i <= 255; i++)
            {
                Start(String.Format("192.168.100.{0}", i));
            }
        }

Answer 3

The previous answer was correct (though it didn't touch on a more advanced point that you will ultimately need to learn ... delegation and invocation ... long story ... won't bore you now).

What you wrote distills to this:

// SIDE NOTE: you cannot actually treat an IPv4 address as four "pure" quads (but that's not your question)

var notNecessarilyAHost = splitGatewayIP[3];
var searchStart = Convert.ToInt32(notNecessarilyAHost);
for (var i = searchStart; i <= searchLimit; ++i)
{
    if (PingHostSweep(gatewayIPRebuild + i))
    {
        return $"{gatewayIPRebuild}{i} ACTIVE";
    }
    else
    {
        return $"{gatewayIPRebuild}{i} CLOSED";
    }
}

...and if you (mentally) step through what you wrote it's fairly straightforward to see that the loop will only ever cycle once. Upon entry to the loop i will be equal to whatever searchStart is. Then you enter the if test. If that test is true, you fall into the true side of the branch (ie, "...ACTIVE"). Otherwise, you'll drop into the else branch (ie, "...CLOSED". FROM THERE...

You ALWAYS return. That will exit the loop (and the function that contains it). You will never cycle the loop again. "break" and "return" (and plausibly goto ... but that's for a different day) will ALWAYS exit the current scope (scope being a block of code wrapped by '{' and '}' (be they explicitly or implicitly written).

Following?

The previous answer was correct. It adjusts your code so that the loop adds the string you're composing with each iteration to a list of strings. Then, when you exit the loop (because i reaches searchLimit) that list of strings will contain N many, well, strings. You probably want to return or continue working that.

All that said, you can't (technically you can but you SHOULDN'T) do any of this inside a UI thread. If you do, the UI will block (and become 100% unresponsive to the user) while the loop runs (and the network calls that it makes run), etc.