Competitive pricing
No set-up Charges
Over 99.99% Availability
Free Trial Software
Free Technical Support
Try before you buy
Local or Internet Data
Reseller Opportunities
    Postcode finder using data supplied by royal mail
Updated Daily

Postcode Programming API Get Long/Lat from COM Object using PostZon Data:

To get a "Postzon" Geographical Data address from our COM Object we do the following:

Distance between two postcodes

The distance between two postcodes can be returned. Simply call with Postcode and “Home postcode” provided in the parameters. Our service will then return the distance in km.  So approximate charges could be applied to a customer based on the straight line distance.

Postcode to Longitude/Latitude

This is the main use of PostZon data. Simply call with the target Postcode and the PostZon data service will return the Longitude and Latitude. Ideal for mapping and calculating distances.

Getting PostZon Data using the .Net Assembly

Step 1 Sign up for trial

Simply use the "Sign Up for Trial" link at top right of this page to open a trial account.   We will then send you a data key, which is used to identify your account, when using the following service.

Step 2 Download .Net Assembly

The .NET Assembly is for use with any Desktop .NET project.  It is written in Framework V2.0 so compatible with any framework from 2 upwards. It is almost identical to our COM object, but is implemented as a .NET Assembly.  It is therefore easier to distribute within your .NET project, since it requires no extra files.

The .NET Assembly is in the “NET Assembly” directory of our example code.

How to distribute .NET Assembly

Simply include the “ISimplyPostCodeClass.dll” in your application directory.

Note: the .Net Assembly is for desktop applications compiled to 32 bits. It will run fine on 64 bit machines, but will not support an application compiled to 64 bits, as it uses Microsoft MDAC which does not support 64 bits.

Step 3 Creating the .NET Assembly

Copy the “ISimplyPostCodeClass.dll” in your application directory, and then add it to your project references. This can be found in the “NET Assembly” directory of our example code.

In C# or VB, simply right click on the project in the Solution Explorer. Select “Add Reference”. On the window that opens, click on the Browser tab. Now find and double click on “ISimplyPostCodeClass.dll” to add reference.

The class constructor takes a parameter of a working directory PATH. This directory is used to store the advanced search data used in combos if used. This must be a valid directory, and have WRITE permissions.


Public Class Form1
   Public SimplyPostCodeLookup As ISimplyPostCodeClass.ISimplyPostCodeClass

Private Sub Form1_Disposed(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Disposed
   SimplyPostCodeLookup = Nothing
End Sub

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

   SimplyPostCodeLookup = New ISimplyPostCodeClass.ISimplyPostCodeClass(CurDir)

  C# .NET

public partial class Form1 : Form

   private ISimplyPostCodeClass.ISimplyPostCodeClass SimplyPostCodeLookup;

private void Form1_Load(object sender, EventArgs e)

  string workingDirectoryForWorkingFiles = Directory.GetCurrentDirectory();
   SimplyPostCodeLookup = new ISimplyPostCodeClass.ISimplyPostCodeClass(workingDirectoryForWorkingFiles);


Step 4 Specify the Data Key

The Data Key will have been sent to you via an e-mail when you opened the account. It is also available under the “Data Key” tab of the online admin window.  For the .NET Assembly you should use the data key beginning with "I_".



  C# .NET

string DataKey="Your Data Key";
SimplyPostCodeLookup.SetDataKey(ref DataKey);

Step 5 Call GetPostZonAddressRecord to get PostZon record

Simply call GetPostZonAddressRecord (Postcode) as Boolean

This call will retrieve the PostZon Data for a given Postcode, OSRef, Longitude/Latitude or "Town, County". This PostZon data is collected from many different source by the Royal mail. The most useful information is Distance from Home Postcode (in Kilometers), Longitude and Latitude.

  This call can be used with Local Data or Internet based data. 

To get the PostZon record by OSRef, simply set postcode to the OSRef, when calling GetPostZonData.

To get the PostZon record by Longtitude/Latitude, (closest within 10Km) set postcode to the "Longtitude|Latitude" (separated by |).

Postcode Lookup Example:

This code will get PostZon data from our database:


'Set Data key, to identify your account
SimplyPostCodeLookup.SetDataKey("Your Date Key")

With SimplyPostCodeLookup
   'Set optional Home Postcode to get straight line distance

   If .GetPostZonAddressRecord(Me.txtPostcode.Text) Then
      Long = .PostZon_Longitude_wgs84
      Lat = .PostZon_Latitude_wgs84
      Distance = .PostZon_DistanceToHomePostcode

      MsgBox(.General_credits_display_text & vbCrLf & .General_errormessage, vbCritical,
                           "Simply Postcode Lookup")

   End If

   Me.Text = "Simply Postcode Lookup : " & .General_credits_display_text
End With

  C# .NET

//Set Data key, to identify your account
string DataKey;
DataKey = "Your Date Key";

//Set optional Home Postcode to get straight line distance
string OptionalHomePostCode =txtHomePostcode.Text;

string PostCodeToFind = txtPostcode.Text;
if (SimplyPostCodeLookup.GetPostZonAddressRecord(PostCodeToFind) == true)
   //Return PostZon data
   Lat = SimplyPostCodeLookup.PostZon_Latitude_wgs84;
   Long = SimplyPostCodeLookup.PostZon_Longitude_wgs84;
   Distance = SimplyPostCodeLookup.PostZon_DistanceToHomePostcode;
   if (SimplyPostCodeLookup.General_errormessage != "")
      MessageBox.Show(SimplyPostCodeLookup.General_credits_display_text + " " + 
                    SimplyPostCodeLookup.General_errormessage, "Simply Postcode Lookup");

      MessageBox.Show("Not found!");

this.Text = "Simply Postcode Lookup : " + SimplyPostCodeLookup.General_credits_display_text;

To get distance between two points

Simply call:

GetDistance(Latitude1, Longtitude1, Latitude2, Longtitude2) As Double

Step 4 Testing

Final step is to test, to enable easy testing please use our special test postcodes.

PostZon Geographic data - Example Code 

Simply download the example code.   The code is in the "NET assembly/Csharp NET Assembly Example" or "NET assembly/VB NET Assembly Example" directory of our example downloads.

These two examples demonstrate postcode lookup software using PostZon data.

Data Returned:

This type of license returns: (see example below)

Public PostZon_IntroductionDate As String
Public PostZon_Gridrefeast As String
Public PostZon_Gridrefnorth As String
Public PostZon_County As String
Public PostZon_District As String
Public PostZon_Ward As String
Public PostZon_Usertype As String
Public PostZon_Gridstatus As String (accuracy of the geographic data)
Public PostZon_Country As String
Public PostZon_Wardstatus As String
Public PostZon_NHS_code As String
Public PostZon_NHS_region As String
Public PostZon_Latitude_wgs84 As String
Public PostZon_Longitude_wgs84 As String
Public PostZon_OSreference As String
'This is not supported at present but may be in future
Public PostZon_DistanceToHomePostcode As String
'Distance from Home Postcode   

More infromation on Geographic data returned by API