Consuming Yahoo Local Search Service in VB.NET

Introduction:

Yahoo's Local Search Service is provided free of charge to developers through the Yahoo Developer's Network. This article will demonstrate one approach that may be used to consume this service to return a list of business locations through the use of a zip code based search for a business name or product. 

The service returns the following information:

• Title (the name of the business)
• Street Address
• City
• State
• Phone Number
• Latitude and Longitude
• The distance from the center of the zip code supplied by the user
• URLs for maps and details about the business
• URL of the business web site (if available)

This article will demonstrate the basics of submitting Local Search Service request, displaying the results, and accessing the available links returned in the search results. Naturally there are a number of ways in which could present the search results and this demonstration application only illustrates one such possibility. For more information regarding the program refer directly the Yahoo Developer Network website located at http://developer.yahoo.com/dotnet/.

The service may be accessed up to 50,000 times a day; participation in the program is free and is contingent upon signing up for the Yahoo. Developers Network and obtaining an application ID from Yahoo.

When visiting the Yahoo site, take a look at the different programs available and take a look at some of the many services made available through Yahoo.

Figure 1: The demonstration application running



Figure 2: Providing Context Menu Access to the Map, Business, and Business details URLs



Figure 3: Displaying the Map to the Business



Figure 4: Displaying the Business Website



Figure 5: Displaying the Yahoo Business Details

Getting Started:

In order to get started, unzip the included project and open the solution in the Visual Studio 2005 environment. In the solution explorer.

The Main Form (frmSearch.vb)

The main form (frmSearch.vb) is the only form contained in the application; all of the application specific code required to access the service, return the results of an local search, and to display those results in a datagridview control or as a web page are included in this class.

The code is pretty simple, if you'd care to open the code view up in the IDE you will see that the code file begins as follows:

''' <summary>

''' Consume the Yahoo Local Search Service

''' in a Visual Basic Win Forms application

''' </summary>

''' <remarks></remarks>

Public Class frmSearch
 

    ''' <summary>

    ''' Default Constructor

    ''' </summary>

    ''' <remarks></remarks>

    Public Sub New()

 

        ' This call is required by the Windows Form Designer.

        InitializeComponent()

 

        ' the user's zip code likely won't change so

        ' set the zip code to user last entered zip code

        Me.txtZipCode.Text = My.MySettings.Default.MyZipCode
    End Sub

Note that in the constructor, the zip code textbox control is populated from a user setting stored in the application. Each time the user changes the zip code, the last entered zip code is stored in this setting and the next time the application is used, the last zip code is restored into the textbox.

Next section of code is the button click event handler for the search button. When this button is clicked, the method will verify that the user has entered a search term and zip code, will store the current zip code into the user setting (in case the user changed it) and then will call a separate method called Local search which accepts two arguments: the title of the business or product name, and the zip code. 
 

''' <summary>

''' Initiate a Yahoo Local Search Service

''' request based upon the user supplied

''' product/business name and zip code

''' </summary>

''' <param name="sender"></param>

''' <param name="e"></param>

''' <remarks></remarks>

Private Sub btnSearch_Click(ByVal sender As System.Object, _ByVal e As System.EventArgs)Handles btnSearch.Click

 

    ' validate that search terms were entered

    ' by making sure that the business/product

    ' and the zip code textboxes contain something

    If txtBusinessOrProduct.Text <> String.Empty Or _txtZipCode.Text <> String.Empty Then

 

        ' save last entered zip code in user setting

        ' so that the next time the application is used

        ' we can retrieve this zip code and reuse it

        My.MySettings.Default.MyZipCode = txtZipCode.Text

        My.MySettings.Default.Save()

 

        ' call the search with the product and zip code arguments

        ' this function will populate the datagrid with the

        ' values returned from the product search

        LocalSearch(txtBusinessOrProduct.Text, txtZipCode.Text)
 

    Else

 

        ' tell the user that the search requested is invalid

        ' if they failed to fill in both the product/business and

        ' zip code textboxes

        MessageBox.Show("You must supply both a zip code and product/business name.", "Search Invalid")

    End If 
End Sub

The next section of the code is used to execute the local search. The first part of the code stores the business or product name into a string variable and then trims the zip code string to prevent a zip+4 entry; the textbox that accepts the zip code is limited to only five characters in length so this is not really necessary. An Http web request is then formatted to execute the search against the Yahoo Local Search service; this request uses the supplied business or product name along with the supplied zip code to limit the number of results returned. The service limits the results to a maximum of 20 entries.

The derived response stream is used to populate a dataset; the dataset's second table is then bound to the datagridview. The second table contains the results of the search; a total of three tables are returned by the service and contain information regarding the business rating and the total number of hits returned by the search.

 

''' <summary>

''' Conduct a search for products or business names

''' within a specified zip code using the Yahoo

''' Local Search Service

''' </summary>

''' <remarks></remarks>

Private Sub LocalSearch(ByVal business As String, _ByVal zipCode As String)

 

    Try

 

        ' business or product name

        Dim biz As String = business

 

        ' take only the zip code (not zip + 4)

        Dim zip As String = zipCode.Substring(0, 5)

 

        ' format the web request using

        ' the zip code and business/product name

        ' passed in as arguments

        ' NOTE: The appid should be replaced with the

        ' appid supplied by Yahoo when the developer

        ' signs up with the free developer network

        Dim request As System.Net.HttpWebRequest _= System.Net.WebRequest.Create
        ( _"http://local.yahooapis.com/LocalSearchService/V2/localSearch?appid=YahooDemo&query=" _+ biz + "&zip=" + zip +  
        "&results=20")

 

        ' get http web response for the web request

        Using response As System.Net.HttpWebResponse = _equest.GetResponse()

 

            ' populate the dataset using the

            ' response stream (in XML)

            Dim dsSearch As DataSet = New DataSet()

            dsSearch.ReadXml(response.GetResponseStream())

 

            ' populate the datagridview control using the

            ' second table (which contains the actual search

            ' results - in all three tables are returned

            dataGridView1.DataSource = dsSearch.Tables(1)

            dataGridView1.Refresh()

 

        End Using

 

    Catch ex As Exception

 

        ' describe any encoutered error if the

        ' local search should fail for any reason

        MessageBox.Show(ex.Message, "Error")

 

    End Try
End Sub

The final three methods contained in the class are used to open up the business, map, and details links provided in the results obtained for any specific business.
 

''' <summary>

''' Open the Map URL for the currently selected row

''' contained in the results datagridview control

''' </summary>

''' <param name="sender"></param>

''' <param name="e"></param>

''' <remarks></remarks>

Private Sub mapURLToolStripMenuItem_Click(ByVal sender As System.Object,ByVal e AsSystem.EventArgs) Handles mapURLToolStripMenuItem.Click

 

    Try

        ' get the cell value for the map URL

        Dim url As String

        url = dataGridView1.SelectedRows(0).Cells(10).Value.ToString()

 

        ' open the URL into a browser window

        System.Diagnostics.Process.Start(url)

 

    Catch

        ' display an error message to the user

        ' if the URL does not exist or was invalid

        MessageBox.Show("Invalid or Missing URL", "Map URL Error")

    End Try 

End Sub 

 

''' <summary>

''' Open the Business URL for the currently selected row

''' contained in the results datagridview control

''' </summary>

''' <param name="sender"></param>

''' <param name="e"></param>

''' <remarks></remarks>

Private Sub businessURLToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e AsSystem.EventArgs) Handles businessURLToolStripMenuItem.Click()

 

    Try

        ' get the cell value for the map URL

        Dim url As String

        url = dataGridView1.SelectedRows(0).Cells(11).Value.ToString()

 

        ' open the URL into a browser window

        System.Diagnostics.Process.Start(url)

 

    Catch

        ' display an error message to the user

        ' if the URL does not exist or was invalid

        MessageBox.Show("Invalid or Missing URL", "Business URL Error")

    End Try 

End Sub 

 

''' <summary>

''' Open the Business Details URL for the currently selected row

''' contained in the results datagridview control

''' </summary>

''' <param name="sender"></param>

''' <param name="e"></param>

''' <remarks></remarks>

Private Sub detailsToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e AsSystem.EventArgs) Handles detailsToolStripMenuItem.Click

 

    Try

        ' get the cell value for the map URL

        Dim url As String

        url = dataGridView1.SelectedRows(0).Cells(8).Value.ToString()

 

        ' open the URL into a browser window

        System.Diagnostics.Process.Start(url)

 

    Catch

        ' display an error message to the user

        ' if the URL does not exist or was invalid

        MessageBox.Show("Invalid or Missing URL", "Business Details URL Error")"

    End Try 

End Sub

Summary

This application was provided as an example of how one might take advantage of the Yahoo Local Search service in a Visual Basic Win Forms application. The service returns information about the business and returns a collection of links that may be used to display a map of the business, the business web site, and Yahoo collected information pertaining to the business.