Create a Flexible Query Application

1. Find Visual Studio in your Start Menu.

2. Right click Visual Studio.

3. In the dropdown menu click Run as administrator.

4. When asked if you want to allow this program (devenv.exe) to make changes to your computer click Yes.

1. On the Visual Studio Start Page select New Project….

2. Select Visual C# and Console Application (Visual Basic and Console Application if you prefer Visual Basic) in the New Project dialog.

3. From the left drop-down list at the top of the New Project dialog box, select .NET Framework 4.

   Visual Studio 2010 defaults to .NET Framework 4. If you use an earlier version of Visual Studio and do not have .NET Framework 4 installed go to the .NET Framework 4 download page to download and install it.

4. Give your project a meaningful name. For example, for this project you could name it USCrime2006and2007.

5. Click OK.

6. Add the following code to the top of Program.cs (Program.vb) which is needed to authenticate your access to the dataset.

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   using System.Net; // needed for authentication
   

1. Go to the Marketplace home page.

2. Click the My Data tab.

3. Find the 2006 - 2008 Crime in the United States data service.

4. Click Use to the right of the dataset name. This takes you to the Details Page. for this dataset.

5. Scroll down the page to the tabs below Learn How to Use this Data in Visual Studio

6. Click the Details tab.

7. Find the Service root URL.

   

   
   Figure 1 – Service root URL

8. Copy the Service root URL to your clipboard.

1. Return to your Visual Studio project.

2. In Solution Explorer right click References.

3. Select Add Service Reference… from the dropdown menu.

4. Paste the Service root URL from your clipboard in the Address dropdown.

5. Click Go.
   Wait a few moments for the Services text box to populate with the service available to your project.

6. Enter a meaningful namespace name in the Namespace textbox.
   For Example: DataGovCrimes.

7. Click OK.
   The name of your service reference will appear under Service References in Solution Explorer.

1. Select Program.cs (Program.vb) in the Visual Studio Code Pane.

2. Add the following statement which makes your service reference accessible to your application.

   Note
   Use the program namespace plus the service reference namespace name you created in #6 above.

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   using USCrime2006and2007.DataGovCrimes; // using ApplicationName.ServiceReferenceName
   

1. Create a public class, CrimeData, within your project namespace.

2. Create two private variables within your class.

   • A Uri to the service.
     
     
   • A service container that stores your service credentials in the service context.
     
     

     Find the Entity type

     1. Go to the “Details Page.”

     2. Click Get Started with this Dataset.

     3. Click the Overview tab.
        The entity set name and entity collection name are displayed.

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   class CrimeData
   {
       private Uri serviceURI;
       private datagovCrimesContainer context;
   }  // end class CrimeData
   
   

3. Create a constructor for the CrimeData class.
   The constructor initializes both private variables and initializes user credentials.
   The SERVICE_ROOT_URL is the https link you copied to your clipboard above. (See Get the Service Root URL.)
   The context is the service container which is used for user credentials.
   The IgnoreMissingProperties property is set to true to make the client robust to properties being added to the type on the server. (See MSDN documentation for additional information.)
   The USER_ID is your Live ID.
   The SECURE_ACCOUNT_KEY is the Marketplace account key you’re using for this application. (See Manage Your Marketplace Account.)

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   class CrimeData
   {
       private Uri serviceURI;
       private datagovCrimesContainer context;
   
       // constructor for the CrimeData class
       public CrimeData()  
       {
           serviceURI = new Uri(SERVICE_ROOT_URL);
           context = new datagovCrimesContainer(serviceURI);
           context.IgnoreMissingProperties = true;
           context.Credentials = new NetworkCredential(USER_ID,
                                                       SECURE_ACCOUNT_ID); // Your Marketplace account key
       }  // end constructor
   
   }  // end class CrimeData
   
   

4. Create a public method within your class that returns a generic list. For our program the generic list type is CityCrime.
   This method queries the service and if successful returns the result set as a list. If the query fails for any reason the method returns a null (Nothing).

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   class CrimeData
   {
       private Uri serviceURI;
       private datagovCrimesContainer context;
   
       // constructor for the CrimeData class
       public CrimeData()
       {
           serviceURI = new Uri(SERVICE_ROOT_URL);
           context = new datagovCrimesContainer(serviceURI);
           context.IgnoreMissingProperties = true;
           context.Credentials = new NetworkCredential(USER_ID,
                                                       SECURE_ACCOUNT_ID);
       }  // end constructor
   
       // -- public method that returns a list of crime data
       public IList<CityCrime> GetCrimeData()
       {
           IEnumerable<CityCrime> query = context.CityCrime.Where(crime => crime.City == "Newport").OrderBy(crime => crime.Year);
   
           try
           {
               return query.ToList();
           }
           catch (Exception ex)
           {
               Console.WriteLine("Error: {0}", ex.Message);
               return null;
           }  // end try
   
       }  // end function GetCrimeData
   
   }  // end class CrimeData
   
   

   The query can be any valid Marketplace LINQ query and may optionally include the where (Where) filter and/or orderby (Order By).
   For more information on LINQ queries see LINQ Query Expressions (C# Programming Guide) (LINQ in Visual Basic).
   For information on LINQ query limitations within the Marketplace see Supported OData Query Options.

   The following LINQ queries are valid within the Marketplace.

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   query = from crimes in context.CityCrime
               where crimes.City == "Newport" 
               orderby crimes.Year Ascending
               select crimes;
   //  this query could also be written as
   //  IEnumerable<CityCrime> query = context.CityCrime.Where(crime => crime.City == "Newport").OrderBy(crime => crime.Year);
   
   

5. Write the code in Main() that utilizes your CrimeData class and GetCrimeData() method to consume the data and display it.

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   using System.Net;
   using USCrime2006and2007.DataGovCrimes; // using ApplicationName.ServiceReferenceName
   
   namespace USCrime2006and2007
   {
      class Program
      {
         public static void Main(string[] args)
         {
             IList<CityCrime> crimeList;  // CityCrime is the entity type returned by the service
             CrimeData crimeData = new CrimeData();
   
             crimeList = crimeData.GetCrimeData();
   
             if (crimeList != null)
             {
                 Console.WriteLine("{0,4} {1,-12} {2,-15} {3,10} {4,13}","Year",
                                                                         "City",
                                                                         "State",
                                                                         "Population",
                                                                         "Violent Crime");
   
                 foreach (CityCrime c in crimeList)
                 {
                     Console.WriteLine("{0,4} {1,-12} {2,-15} {3,10} {4,13}", c.Year, 
                                                                              c.City, 
                                                                              c.State, 
                                                                              c.Population,
                                                                              c.ViolentCrime);
                 } // end foreach
   
             }  // end if
   
             Console.Write("Tap any key to exit. ");
             Console.ReadKey();
   
         }  // end Main
   
       }  // end class Program
   
   }  // end namespace
   
   

The dataset’s metadata informs intellisense as you write your code. If your IDE does not support intellisense or intellisense fails to work you can get the metadata from the service.