Before I go ahead and explain this behavior a little background on sp_executesql. The sp_executesql comes into play when there is a client side parameterization helping in the re-use of one parameterized compiled plan. More information about Query Parameterization here . When there is no parameter specified then SQL Server tries to do an auto parameterization helping in reuse of query plan.

It appears that the decision to use sp_executesql or a direct sql batch is governed by ADO.Net’s SQLCommand object. It appears per the Tabular Data Stream (TDS) there’s only 2 ways to execute a SQL query – use RPC to execute SQL stored procedure and use SQL Batch for T-SQL. So when we have a parameterized query we tend to use RPC and call sp_executesql.

Now coming back to Entity Framework. A query like this

var cust = from c in ctx.Customers

           where c.CustomerID == "ALFKI"

           select c;

would produce the following T-SQL

SELECT 

[Extent1].[CustomerID] AS [CustomerID], 

[Extent1].[CompanyName] AS [CompanyName], 

[Extent1].[ContactName] AS [ContactName], 

[Extent1].[ContactTitle] AS [ContactTitle], 

[Extent1].[Address] AS [Address], 

[Extent1].[City] AS [City], 

[Extent1].[Region] AS [Region], 

[Extent1].[PostalCode] AS [PostalCode], 

[Extent1].[Country] AS [Country], 

[Extent1].[Phone] AS [Phone], 

[Extent1].[Fax] AS [Fax]

FROM [dbo].[Customers] AS [Extent1]

WHERE N'ALFKI' = [Extent1].[CustomerID]

This is so because we have a constant value for the parameter will not change and hence there is a direct SQLBatch generated. 
Note that at the SQL Server end this will get converted into an auto parameterized query. 

However, a query like this 

string CustID = "ALFKI";

                var cust = from c in ctx.Customers

                           where c.CustomerID == CustID

                           select c;

 Would generate the following query

exec sp_executesql N'SELECT 

[Extent1].[CustomerID] AS [CustomerID], 

[Extent1].[CompanyName] AS [CompanyName], 

[Extent1].[ContactName] AS [ContactName], 

[Extent1].[ContactTitle] AS [ContactTitle], 

[Extent1].[Address] AS [Address], 

[Extent1].[City] AS [City], 

[Extent1].[Region] AS [Region], 

[Extent1].[PostalCode] AS [PostalCode], 

[Extent1].[Country] AS [Country], 

[Extent1].[Phone] AS [Phone], 

[Extent1].[Fax] AS [Fax]

FROM [dbo].[Customers] AS [Extent1]

WHERE [Extent1].[CustomerID] = @p__linq__0',N'@p__linq__0 nvarchar(4000)',@p__linq__0=N'ALFKI'

Background

Lets take a look at the following code for querying the EntitySet in EF v3.5

 using (NorthwindEntities ex = new NorthwindEntities())

            {

                var cus = ex.Customers;

                foreach (var c in cus)

                {

                    //do some operation here             

                }

            }

As you see here the type resolved is ObjectQuery<NorthwindModel.Customers>. And the major design hit was that if you were to do some CUD(Create,Update and Delete) operation in the pre EF v4 world, you had to depend upon ObjectContext rather than perfoming them on the Object itself. So we had to write the following code for the Create operation

//create a new customer      

Customers newCustomer = new Customers();    

 newCustomer.ContactName = "Xyz";       

 //fill the rest details of the customer

 //...   

//add the new customer to the context  

 ex.AddToCustomers(newCustomer); 

//persist changes 

 ex.SaveChanges();

 

Outcome

In EFv4, ObjectSet was introduced. ObjectSet is an extension to ObjectQuery and has the following graph of inheritance

This gives power to the EntitySet to do the  CUD operations that were only available in the ObjectContext before. So now the above code for adding a Customer entity will look like this

 using (NorthwindEntities ex = new NorthwindEntities())            

 {              

 Customer newCustomer = new Customer();

 newCustomer.ContactName = "Xyz";       

 ex.Customers.AddObject(newCustomer);  

 ex.SaveChanges();       

 }

Its relatively easy to do this , the steps would be

• Make a connection to the DataService using Data Service client API
• Get the Data as a collection , my favorite List<T> :)
• Add it to the ReportDataSource and bind it to the LocalReport

However, regarding the parameter passing , we know that if we add a parameter to the local report it does not prompt for the user and the developer is responsible for getting the value. Also you need to decide whether you need to get the entire data on the client and then do a filter on it or if  you want to get the filtered data from the server based on the parameter selected from the client. I took the former approach and get the entire data(considering the small amount of data that I have ). Here is how

I am assuming that you already have a neat WCF Data Service defined and ready to take the requests, in this case at http://localhost:54560/MyDataService/NorthwindService.svc/ . If you are new to this then I suggest you take a look at Getting Started with Data Services section on MSDN

In order to code the client lets first create a Data Service proxy using the tool DataSvcUtil.exe . Open up Visual Studio command prompt and type the following

c:\Users\bindeshv>DataSvcUtil /out:NorthwindService.cs /language:CSharp /uri:http://localhost:54560/MyDataService/NorthwindService.svc/

Next go ahead and add this to your WinForms project as an existing item. Once done you need to add the Using reference to the newly added chsarp namespace.

Add a RDLC file to the project as shown below

Next we need to define the data source for the local report. In order to do that bring up the Data Sources explore (from Visual Studio Menu , Data > Show Data Sources) and then click on Add New Data Source in the Data Source Explorer. This will start a wizard and in the first window choose Service as the Data Source type and in the next window type in the url of your WCF Data Service as shown below and click Go

Go ahead and give a namespace and then click on OK button.  Once the service reference is added to the project and since WCF Data Services exposes entity you need to choose the object that you will bind the report to. In order to do this again go to the Data Source Explorer and then Add a new Data Source but this time choose Object instead of service and point it to the WCF Service that was added to the project like shown below

Once the object is added to the Data Source Explore you can proceed with the normal design of the report by dragging in a table component and then adding the necessary fields

Now we need to add the Report Parameter, in this case I will specify the Employee ID as input for filtering , so that we see details of only one specific employee. In the Visual Studio Menu option go ahead and chose Report > Report Parameters..  and the required parameter

Once the parameter is defined you need to specify it in the Reports Table Properties Filter section as shown below

Once the filtering is done go ahead and add a Report Viewer control to the form. Remember we need to device our own parameter for Reports in case of local report. Here is how my form looks after the design is done

And here is how the code behind looks like

       //Form level member
       private List<Employees> empList = null ;

       private void Form1_Load(object sender, EventArgs e)
        {
            if (empList == null)
            {

                NorthwindModel.NorthwindEntities entitiesContext = new NorthwindModel.NorthwindEntities(new Uri("http://localhost:54560/MyDataService/NorthwindService.svc/"));
                try
                {

                   empList = (from emps in entitiesContext.Employees
                               select emps).ToList<Employees>();
                

                    ReportDataSource rds = new ReportDataSource("DataServiceForms_NorthwindReference_Employees", empList);
                    this.reportViewer1.LocalReport.DataSources.Clear();
                    this.reportViewer1.LocalReport.DataSources.Add(rds);

                }

                    
                catch (Exception _ex)
                {
                    MessageBox.Show(_ex.Message);

                }
            }

            //get all the employee ids and bind it 

            var empIDs = from emps in empList
                         select emps.EmployeeID;
            foreach (int i in empIDs)
            {
                this.comboBox1.Items.Add(i);
            }
            //set the combo to display the first item
            this.comboBox1.SelectedIndex = 0;

            //bind parameters to the report
            BindParameter();
        }

      private void BindParameter()
       {
           ReportParameter param = new ReportParameter("EmpID", this.comboBox1.SelectedItem.ToString());
           this.reportViewer1.LocalReport.SetParameters(new ReportParameter[] { param });
           this.reportViewer1.RefreshReport();
       }

       private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
       {
           BindParameter();
       }

The completed report looks like this

Until next post ..

"The specified named connection is either not found in the configuration, not intended to be used with the EntityClient provider, or not valid."

If you go check the EntityProject you might find the connectionstring information inside the app.config. This is created automatically by the Entity Model Designer wizard. The issue is that when you refer the EntityProject inside another project the dll for the entity model is loaded in the context of the current application and hence it tries to read the connectionstring from the current app.config/web.config file.

The fix is to add the connectionstring information from the EntityProject  to your referring project’s app.config or web.config under the <connectionstrings> element , like this

<connectionStrings>
   <add name="SchoolEntities" connectionString="metadata=res://*/SchoolModel.csdl|res://*/SchoolModel.ssdl|res://*/SchoolModel.msl;provider=System.Data.SqlClient;provider connection string=&quot;Data Source=.\yukon;Initial Catalog=School;Integrated Security=True;MultipleActiveResultSets=True&quot;" providerName="System.Data.EntityClient" />
</connectionStrings>

Here is the forum post on this http://social.msdn.microsoft.com/Forums/en-US/adodotnetentityframework/thread/d0261818-ed96-43b6-adfd-3c146d8e1a68/

There were a couple of issues that I faced in getting it to run especially with changes in WCF and EF 3.5 sp1. So I thought of blogging about this to help get this working without much hassles.

Changes Needed In EntityBag

The first issue that you will face while compiling EntityBag project(Perseus) is the following error

  No overload for method 'GetEntityKey' takes '2' arguments        C:\Users\bindeshv\Code\perseus-1.1 entitybag\Perseus\UtilityExtensionMethods.cs     

The above error happens because ObjectContext.GetEntityKey(entitySetName, object) was a beta 3 method which was removed. Though there is an extension method inside UtilityExtensionMethod.cs  for IRleatedEnd like this

      public static EntityKey GetEntityKey(thisIRelatedEnd relatedEnd)
       {
           Debug.Assert(relatedEnd.IsEntityReference());
           TyperelationshipType = relatedEnd.GetType();
           PropertyInfo pi = relationshipType.GetProperty("EntityKey");
           return(EntityKey)pi.GetValue(relatedEnd, null);
       }

But the actual code calling this method is on ObjectContext in our CreateOriginalValuesObject method like this

      EntityKey targetKey = context.GetEntityKey(fullEntitySetName, target);

Since the intent here was to get the entity key for the target object and then get its ObjectStateEntry and then clone the original entries in the source to target, I changed the code to like this 

          // EntityKey targetKey = context.GetEntityKey(target);
            ObjectStateEntry targetStateEntry = context.ObjectStateManager.GetObjectStateEntry(target);

Changes In WCF Service

To test the program I created the following service contract and tried exposing it over WsHttpbinding

   [ServiceContract]
   public interface INorthwind
  {
      [OperationContract]
       EntityBag<NorthwindModel.Customers> GetCustomerByID(string customerID);

      [OperationContract]
      void UpdateCustomer(EntityBag<NorthwindModel.Customers> customers);

      [OperationContract] //for test
      int Test(int p);


  }

But each time I tried getting this over to the client I will get a weird error on the client (took 2 days to figure this out)

An error occurred while receiving the HTTP response to http://binvij-admin2.fareast.corp.microsoft.com/NorthwindSVC/Northwind.svc. This could be due to the service endpoint binding not using the HTTP protocol. This could also be due to an HTTP request context being aborted by the server (possibly due to the service shutting down). See server logs for more details.

Server stack trace:

   at System.ServiceModel.Channels.HttpChannelUtilities.ProcessGetResponseWebException(WebException webException, HttpWebRequest request, HttpAbortReason abortReason)

   at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout)

   at System.ServiceModel.Channels.RequestChannel.Request(Message message, TimeSpan timeout)

   at System.ServiceModel.Channels.ClientReliableChannelBinder`1.RequestClientReliableChannelBinder`1.OnRequest(TRequestChannel channel, Message message, TimeSpan timeout, MaskingMode maskingMode)

   at System.ServiceModel.Channels.ClientReliableChannelBinder`1.Request(Message message, TimeSpan timeout, MaskingMode maskingMode)

   at System.ServiceModel.Channels.ClientReliableChannelBinder`1.Request(Message message, TimeSpan timeout)

   at System.ServiceModel.Security.SecuritySessionClientSettings`1.SecurityRequestSessionChannel.Request(Message message, TimeSpan timeout)

   at System.ServiceModel.Dispatcher.RequestChannelBinder.Request(Message message, TimeSpan timeout)

   at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)

   at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)

   at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)

I implemented a WCF trace, more details here on enabling the trace , and saw the following logged in

<ExceptionType>System.ServiceModel.CommunicationException, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</ExceptionType>

<Message>There was an error while trying to serialize parameter http://tempuri.org/:GetCustomerByIDResult. The InnerException message was 'Type 'NorthwindModel.Customers' with data contract name 'Customers:http://schemas.datacontract.org/2004/07/NorthwindModel' is not expected. Add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.'. Please see InnerException for more details.</Message>

<StackTrace>at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeParameterPart(XmlDictionaryWriter writer, PartInfo part, Object graph) at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeParameter(XmlDictionaryWriter writer, PartInfo part, Object graph) at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeBody(XmlDictionaryWriter writer, MessageVersion version, String action, MessageDescription messageDescription, Object returnValue, Object[] parameters, Boolean isRequest) at System.ServiceModel.Dispatcher.OperationFormatter.SerializeBodyContents(XmlDictionaryWriter writer, MessageVersion version, Object[] parameters, Object returnValue, Boolean isRequest) at

The DataContractSerializer did not know about my Northwind.Customers type so I had to append my ServiceContract with

 [ServiceContract]
 [ServiceKnownType(typeof(NorthwindModel.Customers))]
 
  public interface INorthwind
  {
      [OperationContract]
     
      EntityBag<NorthwindModel.Customers> GetCustomerByID(string customerID);

Note: This is missing in the client test project for EntityBag in the  demo

After this I got an error at the client end, though I could see the WCF service sending the EntityBag<Customers> successfully. Here is the error
 message 

The formatter threw an exception while trying to deserialize the message: There was an error while trying to deserialize parameter http://tempuri.org/:GetCustomerByIDResult. The InnerException message was 'Error in line 1 position 1808. Element 'http://schemas.microsoft.com/2003/10/Serialization/Arrays:anyType' contains data of the 'http://schemas.datacontract.org/2004/07/NorthwindModel:Customers' data contract. The deserializer has no knowledge of any type that maps to this contract. Add the type corresponding to 'Customers' to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding it to the list of known types passed to DataContractSerializer.'.  Please see InnerException for more details.

Server stack trace:

   at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.DeserializeParameterPart(XmlDictionaryReader reader, PartInfo part, Boolean isRequest)

   at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.DeserializeBody(XmlDictionaryReader reader, MessageVersion version, String action, MessageDescription messageDescription, Object[] parameters, Boolean isRequest)

   at System.ServiceModel.Dispatcher.OperationFormatter.DeserializeBodyContents(Message message, Object[] parameters, Boolean isRequest)

   at System.ServiceModel.Dispatcher.OperationFormatter.DeserializeReply(Message message, Object[] parameters)

   at System.ServiceModel.Dispatcher.ProxyOperationRuntime.AfterReply(ProxyRpc& rpc)

   at System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime operation, ProxyRpc& rpc)

   at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)

   at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)

   at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)

We get this error due to an inappropriate setting of the buffer size for the binding in use. Check this link for more details
http://social.msdn.microsoft.com/Forums/en-US/wcf/thread/e0bac3a6-f758-499b-9cab-32435b9887ea

The fix is to increase the messagesize for both the client and the service in the config file

         <wsHttpBinding>
         <binding name="AllowLargeMessages" maxReceivedMessageSize="512000" maxBufferPoolSize="512000" >
           <readerQuotas maxArrayLength="5000000" />
         </binding>
        </wsHttpBinding>

And this should help getting your EntityBag serialized and Deserialized.

Hope this helps !

SQL Server 2008 -Beyond Relational Data by Praveen Srivatsa, Asthrasoft Consulting

XML Feature
We deal with most of the data that is Non Relational in nature

SQL Server 2008 has support for non relational data and it provides various data types

You can use XQuery with Xml type. This allows you to specify a schema as well so you have some control over the type being stored. In general the data can be stored in XML type and retrieved as a relational model or vice versa

Mapping of new date/time data types to xsd types

CLR Feature
Lots of queries around this feature from many people. And I got scared about this atleast from the Support aspect of it . Developers wanted to put many things as a CLR object. And below is my thought about this

Only 13 assemblies are allowed to be used called 'Blessed Assemblies'. UNSAFE load of an assembly can cause SQL Server memory corruption since it loads it inside MTL which is used for by sql server for external hosting of COM,CLR and out process providers

Filestreams
Benefits of filestream against BLOB types explained. Books OnLine(BOL) has more details on this.

ADO.NET Data Services Futures by Harish Ranganathan, Developer Evangelist

This talk was about ADO.Net Data Services offline still under development. Harish showed a smart client which can work offline. This is pretty pre-beta state. There were a lot of queries but most of them I believe would be clear if one goes through the ADO.Net synchronization services like one of the query was how does this handle a conflict of column  here is the MSDN page for this http://msdn.microsoft.com/en-us/library/bb726002.aspx 

One of the interesting questions asked in the session was :-

Can we keep version based copies of the modified records ? As of now I don’t this is thought about , but you can give your feedbacks on the Microsoft Connect site .

Modern Data Access Patterns and Implementations by Don Smith, Program Manager,P&P

This talk was an architect level discussion around the new patterns that should be incorporated for data access in particular with the DDD(Domain Driven Design). There is a lot being discussed about this in the P&P group and they are working on few patterns for data access, the code for which will be released once the VS 2010 beta is available. The pattern thats being explored are

• Unit of work
• ActiveRecords
• Repository pattern
  

Check the codeplex site for more details http://www.codeplex.com/dataguidance

Building scalable applications using Velocity by Abid Khan, Program Manager, Velocity

Velocity is the new kid on the block was distributed caching. Many cool features in particular the load balancing. One of the internals is that this was purely build using .NET FX and leveraging the WCF as the backend for query over NamedPipes channel. Pretty much utilizes most of the concepts from clustering world and automatically detects any offline and online of hosted velocity server. Key takeaways

• As of now it does not invalidate the cache and refresh itself from the database. Going forward this will be thought about
  
• Please use a dedicated servers for velocity rather than clubbing it with the SQL Server or Web Farm
  
• Velocity can be enabled for High Availability where in it will replicate the data across different hosted servers and thus available any time
  
• Can be used in any .net client

Vision/Road Map

• Being able to provide LINQ interfaces to query instead of the traditional get/put methods
  
• Support for non .NET clients like PHP
  
• Availability for HPC (High Performance Computing)

More details here at MSDN site http://msdn.microsoft.com/en-au/data/cc655792.aspx

until next post :)

ASP.NET 4.0 Features from Stephen Walther, Program Manager, ASP.NET

• Source based development, more focus on a neater and readable code
• Asp.net control’s client side ID code looked weird, so if you were using a client side script framework like JQuery it would be difficult to identify the control’s id in case a control lives inside a Master page. In ASP.Net 4.0 there is a property called {Control}.ControlID that will allow to the users to specify a more neater feature
• Auto rendering of the code with "runat=server” attribute once picked from intelli sense  for common controls
• <asp:formview> and <asp:listview> now allows you to render them in div mode apart from the traditional table mode
• Viewstate can be disabled at the page level and then enabled for particular controls .  This is different from the EnableViewState mode since ViewState is inherited to the child controls whereas the EnableViewState does not
• Response.Redirect was not SEO friendly and search engine had issues with indexing them . Now asp.net 4.0 enables you to use Response.PermanentRedirect which emits a status code that is recognized by Search Engines(i believe it is status code 301 if i am remembering this correctly)
• New control added in asp.net 4 –>  QueryExtender . More about this here http://blogs.microsoft.co.il/blogs/bursteg/archive/2009/04/12/asp-net-queryextender-control-and-domaindatasource.aspx
  
• Features added to ASP.Net Core are
• Cache Extensibility using Velocity
• Browser capabilities extensibility
• Session state compression using 2 main industry standards . One of them is GZIP

Some of the interesting questions asked by attendees are and there answers by Stephen

• Can i deploy ASP.NET application to the cloud(Microsoft Azure) ?
    You can use visual studio 2008 azure toolkit to deploy the applications to Azure
  
• When do we use Silverlight vs ASP.NET Web Forms vs ASP.NET MVC vs ASP.Net Ajax
  These are targeted to different needs and hence different problems.
  
• How can i combine some features from asp.net 4.0 and dynamic data . Can we club them ?
  Yes you can.
  
• Check ASP.Net 4.0 and VS 2010 features White paper here http://www.asp.net/learn/whitepapers/aspnet40/

ASP.Net MVC from Stephen Walther

Well most of this talk was a walk through of a demo application and it was quite interesting. Some of the main features from MVC RTM that needs to be mentioned are

• SEO based URLs
  
• PartialAjaxUpdate
  
• Velocity code templates available(this one refers to the java Velocity)
  
• Create your own code generation for View creation using T4 templates

LINQ Deep Drive from Sanjay Vyas

This session was like starting from the beginning like how Linq works. So I am not going to spend time detailing it , there is plenty information already available on the net. I will post some interesting questions asked in the session and my answers to the same

• Is the var keyword reflected at runtime ?
  No, the CompilerService actually converts it to a type but does not give it a name. It actually looks something like this  if you use ILDasm

class [System.Core]System.Func`2<int32,class '<>f__AnonymousType0`1'<int32>> LinqTest.Program::'CS$<>9__CachedAnonymousMethodDelegate4'

• Can we use Linq for existing Datasets ?
  Yes, but only if you compile it with .net 3.5 framework. Here is more details about this on  MSDN http://msdn.microsoft.com/en-us/library/bb386977.aspx 
  
• Whats the benefit of Property initializers , can’t i use constructors instead ?
  In a normal code you can but when you are writing a Linq Select statement and creating a new type the initializer becomes handy
  
• Is the return type of the following query an IList<int> 
  
  List<int>list=newList<int>() {1,2,3,4,5};
                                                                 
             var res=from o in list                     
                       where o >2                       
                      select(new{iVal =o});       

        No, instead would be a type of IEnumerable<int>

• Is there a performance hint while using Linq
  Not that we know of , but in case you find one, send us a repro code with the details of the delay  
  
• What is the difference between IQueryable and IEnumerable
  Graphically put
  
  
  

    Simply put IQueryable allows the mechanism for expression evaluation using queries. IEnumerator allows you to enumerate the collection. IQueryable on evaluation of a query expression gives you back a Enumerator for the resultant collection

Until next post :)

In order to get this working you might need to implement a partial class and then specify the method. So lets take a look at how to use a Sproc that returns a Distinct Country names from Northwind.Customers

CREATE PROCEDURE dbo.GetCountryList
AS
    BEGIN
     SET NOCOUNT ON 
      SELECT DISTINCT COUNTRY FROM CUSTOMERS ORDER BY COUNTRY ASC
     
  END 

First we might need to add the stored procedure inside the EDMX schema as we did in the previous stored procedure demo. So in the Model browser go ahead and the stored procedure by first adding it to Store Model and the adding the Function Import. Here is a screenshot

Notice that I have the return type as Scalar.  This will generate the following CSDL element

<FunctionImport Name="GetCountryList" ReturnType="Collection(String)" /></EntityContainer>

The return type element specify that its a Collection of String. Lets implement the partial class and write the code for calling the stored procedure

public partial class NorthwindEntities :global::System.Data.Objects.ObjectContext
 {
    /// <summary>
    /// Implementation for calling a method that returns distinct country list
    /// </summary>
    /// <returns>String collection </returns>
    public Collection<string> GetCountryList()
    {
        Collection<string> results = new Collection<string>();

        try
        {
            //get the connection object from the DataContext
            using (DbConnection conn = this.Connection)
            {
                DbCommand cmd = conn.CreateCommand();
                //command text is of the format of 'ContainerName.Stored Proc Name' 
                cmd.CommandText = String.Format("{0}.{1}", this.DefaultContainerName, "GetCountryList");
                cmd.CommandType = System.Data.CommandType.StoredProcedure;
                if (this.Connection.State != System.Data.ConnectionState.Open)
                {
                    this.Connection.Open();
                }

                var reader = cmd.ExecuteReader(CommandBehavior.SequentialAccess);
                while (reader.Read())
                {
                    results.Add((string)reader[0]);
                }

                return results;
            }
        }
        catch (Exception ex)
        {
            //Todo: meaning full exception handling 
        }



        return (Collection<string>)null;
       
    }
 }

Once this is compile you will be able to call this method from the front end using intellisense as shown in the screenshot below

Here is the code for forms binding

private void Form1_Load(object sender, EventArgs e)
       {
           using (NorthwindEntities entities = new NorthwindEntities())
           {
               this.customersBindingSource.DataSource = entities.CustByCountry("Germany");
               //bind the combo box
               //get the list of countries
               var countries = entities.GetCountryList();
               //for each country item in countries 
               foreach (var c in countries)
               {
                   //add the country name
                   this.toolStripComboBox1.Items.Add(c);

               }

           }
       }

And here is the output of the forms binding

I have created a Windows based application with Northwind database model(EDMX) . And have the Customer and Orders table selected.

In order to add a stored procedure open up the Model Browser and right click on the Model.Store in this case NorthwindModel.Store

And choose the required stored procedure. Next right click anywhere on the Edmx designer and choose Add > Function Import.

This will bring up the wizard for adding Function. Choose the procedure you had added in the Model Store and choose the return type. In this case Customers which is of type Entity

This step will add a function to the EntityContext class. Here is how the generated code might look like

         /// <summary>
        /// There are no comments for NorthwindModel.CustByCountry in the schema.
        /// </summary>
        public global::System.Data.Objects.ObjectResult<Customers> CustByCountry(string country)
        {
            global::System.Data.Objects.ObjectParameter countryParameter;
            if ((country != null))
            {
                countryParameter = new global::System.Data.Objects.ObjectParameter("Country", country);
            }
            else
            {
                countryParameter = new global::System.Data.Objects.ObjectParameter("Country", typeof(string));
            }
            return base.ExecuteFunction<Customers>("CustByCountry", countryParameter);
        }

In my forms code I use an Object Data Source and have the following code for Forms_Load

          using (NorthwindEntities entities = new NorthwindEntities())
            {
                this.customersBindingSource.DataSource = entities.CustByCountry("Germany");
                
            }

Here is the output

EdmGen is utility shipped with Entity Framework for creation of the artifacts required for Entity Model Mapping viz the CSDL(Conceptual Schema Definition Language), SSDL(Storage Model) and MSL(Mapping Model). Though you can use the EDM wizard in Visual Studio 2008 sp1, but since you may find a lot of references how to use the EDM wizard on internet and really less information on usage of Edmgen, I resorted to this.

Lets see how to create the artifacts for our School Database Model. The School database can be generated from the scripts available at MSDN here. [Creating the School Sample Database http://msdn.microsoft.com/en-us/library/bb399731.aspx]

Open up Visual Studio 2008 Command Prompt and then fire the following command

c:\> edmgen /connectionstring:"server=.\yukon;integrated security=true;database=school" /mode:FullGeneration /project:"EntityClientDemo"

Here is the explanation of  the switches used with Edmgen.exe

• /ConnectionString : specifies the connection string used for connecting to the database
• /FullGeneration : Generate ssdl, msl, csdl, and objects from the database
• /Project : The base name to use for the artifact files.

NOTE: You need to specify either this switch or all the /OutXXXXX switches if you are using the /FullGeneration switch. To get more details on the various switches use EdmGen -help

Next, go ahead and create a new project in Visual Studio 2008. For this post, I created a console application. And add reference System.Data.Entity.

Here is the code

using (EntityConnection conn = new EntityConnection())
           {
               try 
               {
                  conn.ConnectionString =
 @"Metadata=C:\Users\BindeshV\Documents\Visual Studio 2008\Projects\EntityFramework\EFClientDemo\EFClientDemo\Artifacts;" +
 @"Provider=System.Data.SqlClient;"+
 @"Provider Connection String='Server=.\yukon;Integrated Security=yes;Database=School'";
                   conn.Open();
                   EntityCommand cmd = conn.CreateCommand();
                   cmd.CommandText = "Select C.CourseID,C.Title from EFClientDemoContext.Course as C";
                   cmd.CommandType = CommandType.Text;
                   EntityDataReader reader = cmd.ExecuteReader(CommandBehavior.SequentialAccess);

                   while(reader.Read())
                   {
                       Console.WriteLine("Course Id={0} Course Title={1}",reader.GetInt32(0),reader.GetString(1));
                   }
              }
              catch(Exception ex)
               {
                   Console.WriteLine(ex.StackTrace);
               }

           }

           Console.Read();

Usage of EntityClient is somewhat similar to that of the SqlClient.

The ConnectionString property of the EntityConnection object has 3 keywords

• Metadata - The path where are the artifacts reside. In this case the .csdl,.ssdl and msl.
• Provider - The ADO.NET provider used to connect to the Database Store
• Provider Connection String - The regular connection string

Notice that the CommandText uses the format of ContainerName.EntityName . In our case the EdmGen tool had the following information for Container Name

<Schema Namespace="EFClientDemo" Alias="Self" xmlns="http://schemas.microsoft.com/ado/2006/04/edm">
  <EntityContainer Name="EFClientDemoContext">

Here is the output of the program

Thanks