ASP.NET

<asp:EntityDataSource ID="srcCity" runat="server" ContextTypeName="Namespace.Core.Tracking.Domain" EntitySetName="Cities"
EntityTypeFilter="City" Include="Country" AutoGenerateWhereClause="true"/>
       <WhereParameters/>
        <asp:QueryStringParameter Name="Country.ID" Type="Int32"
             QueryStringField="CountryID" />
     </WhereParameters>
</asp:EntityDataSource>

<asp:EntityDataSource ID="srcCountry" runat="server" ContextTypeName="Namespace.Core.Tracking.Domain" 
EntitySetName="Countries" EntityTypeFilter="Country" OrderBy="it.Name"/>

<asp:GridView ID="grid" runat="server" AutoGenerateColumns="False" DataKeyNames="ID" DataSourceID="srcCity">
   <MasterTableView DataSourceID="srcCity" EditMode="InPlace">
      <asp:TemplateField>
            <asp:Label ID="lblName" runat="server" 
                Text='<%# Eval("Country.Name") %>'/>
       </asp:TemplateField>
      <EditItemTemplate>
           <asp:DropDownList ID="lstCountry" runat="server" 
                SelectedValue='<%# Eval("ID") %>'DataSourceID="srcCountry"
                DataTextField="Name" DataValueField="ID"       
                AppendDataBoundItems="true">
                <ListItems>
                    <asp:ListItem Text="" Value="" />
                </ListItems>
           </DropDownList>
      </EditItemTemplate>
  </MasterTableView>
</GridView>

public partial class City : System.Web.UI.Page{
 
   protected void Page_Load(object sender, EventArgs e){
       grid.RowCreated += new GridViewRowEventHandler(grid_RowCreated);
   }

    void grid_RowCreated(object sender, GridViewRowEventArgs e){

       if (e.Row.DataItem != null){
           var city = EntityDataSourceExtensions.GetItemObject<City>(e.Row.DataItem);
       if(city.Country != null) 
          (grid.FindControl("lstCountry")as DropDownList).SelectedValue = city.Country.ID.ToString(); <-- Here I got Exception
      /*
      System.NullReferenceException was unhandled by user code
      Message=Object reference not set to an instance of an object.
      what the problem? I think object casting is true */
         }
    }
}

public static class EntityDataSourceExtensions {

	public static TEntity GetItemObject<TEntity>(object dataItem) where TEntity : class {

		var entity = dataItem as TEntity;

		if(entity != null) 
                    return entity;

		var td = dataItem as System.ComponentModel.ICustomTypeDescriptor;

		if(td != null)
                     return (TEntity)td.GetPropertyOwner(null);


		return null;
	}
}

protected void Button1_Click(object sender, EventArgs e)
    {
        if (FileUpload1.PostedFile.ContentLength>0)
        {
            string filename = Path.GetFileName(FileUpload1.PostedFile.FileName);
            string storagepath = "D:\\Test\\" + filename;
            int contentLen = FileUpload1.PostedFile.ContentLength;
            Byte[] data = new Byte[contentLen];
            FileUpload1.PostedFile.InputStream.Read(data, 0, contentLen);
            savefiletodatabase(data); 
            FileUpload1.SaveAs(storagepath);
        }
    }




 private void savefiletodatabase(byte[] data) 
    {
        SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ToString());
        try
        {
            SqlCommand command = new SqlCommand("INSERT into dbo.test ([file], [filename], [path]) VALUES (@data, '" + FileName + "', '" + FilePath + "')", connection);
            command.Parameters.AddWithValue("data", data);
            connection.Open();
            command.Connection = connection;
            command.ExecuteNonQuery();
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally { connection.Close(); }
    }

protected void LinkButton1_Click(object sender, EventArgs e)
    {
        getfile();
    }



    private void getfile() 
    {
        SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ToString());
        try
        {
            SqlCommand command = new SqlCommand("Select [file] FROM dbo.test where id='" + Id + "'", connection);
            SqlDataReader reader;
            connection.Open();
            command.Connection = connection;
            reader = command.ExecuteReader();
            if (reader.Read())
            {

                byte[] data = (byte[])reader[0];
                Response.ContentType = "application/octet-stream";
                Response.AddHeader("Content-Disposition", "attachment;filename=" + TextBox2.Text);
                Context.Response.BinaryWrite(data);
            }
        }
        catch (Exception ex) 
        { throw ex; }
        finally
        {
            connection.Close();
        }
       
    }

/****** Object:  Table [dbo].[test]    Script Date: 02/13/2010 19:30:06 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[test](
	[file] [varbinary](max) NULL,
	[filename] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
	[path] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
	[id] [int] IDENTITY(1,1) NOT NULL
) ON [PRIMARY]

GO
SET ANSI_PADDING OFF