During my college days we created a project called "Electronic Map Navigator". Its function is to locate the easiest route from Point A to Point B. Those days, creating map enabled application was still a complicated task but not anymore. Today I guess it's as easy as creating your first hello program. The task made easier by the availability of internet, Google Maps, Google Earth and Virtual Earth. On this article, I will show you how to implement google maps on your VB.NET applications (without using Maps API).
Add "Imports System.Text" statement on your VB.NET project
In your main form, add text boxes to hold street, city, state and zip
Add search button for user to click when searching the map. On it's click event put the following codes:
Try Dim streetaddr As String = "" Dim cityaddr As String = "" Dim stateaddr As String = "" Dim zipaddr As String = "" Dim AddrToSearch As New StringBuilder() AddrToSearch.Append("http://maps.google.com/maps?q=")
' if there is street entry If txtStreet.Text <> "" Then streetaddr = txtStreet.Text.Replace(" ", "+") AddrToSearch.Append(street + "," & "+") End If
' if there is city entry If txtCity.Text <> "" Then cityaddr = txtCity.Text.Replace(" ", "+") AddrToSearch.Append(city + "," & "+") End If
' if there is state If txtState.Text <> "" Then stateaddr = txtState.Text.Replace(" ", "+") AddrToSearch.Append(state + "," & "+") End If
' if there is zip code If txtZipCode.Text <> "" Then zipaddr = txtZipCode.Text.ToString() AddrToSearch.Append(zip) End If
' pass the AddrToSearch value to web browser control wbrowser.Navigate(AddrToSearch.ToString())
Catch ex As Exception
MessageBox.Show(ex.Message.ToString(), "Problem encountered while retrieving google map")
End Try
Aside from actual street address of the map, you can also search the map by latitude and longitude
Try Dim latitude As String = "" Dim longitude As String = "" Dim AddrToSearch As New StringBuilder() AddrToSearch.Append("http://maps.google.com/maps?q=")
' if there is latitude If txtLatitude.Text <> "" Then latitude = txtLatitude.Text AddrToSearch.Append(latitude & "%2C") End If
' if there is longitude If txtLongitude .Text <> "" Then longitude = txtLongitude .Text AddrToSearch.Append(longitude) End If
' pass the AddrToSearch value to web browser control wbrowser.Navigate(AddrToSearch.ToString())
Catch ex As Exception
MessageBox.Show(ex.Message.ToString(), "Problem encountered while retrieving google map")
End Try
Since using this method does not require or needs any Google Maps API, you have little or no control on view map controls. These controls are already provided by Google Maps inside your web browser control.
Beside from the security we squeeze from appliance such as firewall and antivirus, it is a must for our applications to have a second layer of defense. Most often than not you already have several company-wide applications that are interconnected to each other. If you have remote offices, your data will be transmitted over broadband network or internet but how sure are you that each of the application is only accepting data from valid sender? For example, a billing software at remote office that transmits payment confirmation to the financial system located at your head office. Fortunately for .NET developers we can make use of digital certificates. Using digital signatures, we can implement the following security check on our example scenario:
Where: App 1 - Billing Software located at the remote office App 2 - Financial System located at the head office
1. App 1 sign the unique message using digital certificate private key. For example: "POST TRANSACTION" 2. App 1 send the digital signature to App 2 (via web service or ftp file) 3. App 2 receives the digital signature and verify command by using digital certificate public key
Let's put it in C# Code:
1. Sign the text or message using digital certificate's private key. You can have set of commands that are expected by the client application.
private byte[] SignCertificate(string text) { // Open certificate store of current user X509Store my = new X509Store(StoreName.My, StoreLocation.CurrentUser); my.Open(OpenFlags.ReadOnly);
// Look for the certificate with specific subject RSACryptoServiceProvider csp = null; foreach (X509Certificate2 cert in my.Certificates) { if (cert.Subject.Contains("CN=WINGROUP\\micwein")) { // retrieve private key csp = (RSACryptoServiceProvider)cert.PrivateKey; } } if (csp == null) { throw new Exception("Valid certificate was not found"); }
// Hash the data SHA1Managed sha1 = new SHA1Managed(); UnicodeEncoding encoding = new UnicodeEncoding(); byte[] data = encoding.GetBytes(text); byte[] hash = sha1.ComputeHash(data);
// Sign the hash return csp.SignHash(hash, CryptoConfig.MapNameToOID("SHA1")); }
2. On your server/listener application, validate the digital signature if correct
private bool VerifyCommand(string text, byte[] signature, string certPath) { // Load the certificate file to use to verify the signature from a file // If using web service or ASP.NET, use: X509Certificate2 cert = new X509Certificate2(Request.ClientCertificate.Certificate); X509Certificate2 cert = new X509Certificate2(certPath);
// Get public key RSACryptoServiceProvider csp = (RSACryptoServiceProvider)cert.PublicKey.Key;
// Hash the text, the text is the expected command by the client application. // Remember hased data cannot be unhash. It is irreversable SHA1Managed sha1 = new SHA1Managed(); UnicodeEncoding encoding = new UnicodeEncoding(); byte[] data = encoding.GetBytes(text); byte[] hash = sha1.ComputeHash(data);
// Verify the signature with the hash return csp.VerifyHash(hash, CryptoConfig.MapNameToOID("SHA1"), signature); }
Here a sample code on how to call VerifyCommand:
//Use the mycert.cer certificate to verify signature and validate it against the allowed commands if (VerifyCommand("POST TRANSACTION", signature, @"C:\mycert.cer")) //POST TRANS { MessageBox.Show("POST command received from remote client...."); } else if (VerifyCommand("CANCEL TRANSACTION", signature, @"C:\mycert.cer")) //CANCEL TRANS { MessageBox.Show("Cancel command received from remote client...."); } else if (VerifyCommand("RETRIEVE TRANSACTION", signature, @"C:\mycert.cer")) //RETRIEVE TRANS { MessageBox.Show("RETRIEVE Transaction received from remote client...."); } else { MessageBox.Show("Signature is not valid"); }
You can pass the signature to client using web service or FTP. You can download the complete sample source code of this article from here
