ASP.NET

function LogOutUser(result, context) {
    alert("test")
    alert(result)
}        

function LogMeOut() {
    LogOutUserCallBack();
}   

string callBackReference = Page.ClientScript.GetCallbackEventReference(this, "arg", "LogOutUser", "", false);
string logoutScript = "function LogOutUserCallBack(arg, context) { " + callBackReference + "; }";
Page.ClientScript.RegisterClientScriptBlock(typeof(Page), "LogOutUserCallBack", logoutScript, true);

Imports System
Imports System.Collections
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Text
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Drawing.Design


<Assembly: TagPrefix("MyApp.WebControls", "SearchGridView")> 
Namespace MyApp.WebControls
#Region "TemplateColumn"
    Public Class NumberColumn
        Implements ITemplate

        Public Sub InstantiateIn(ByVal container As System.Web.UI.Control) Implements System.Web.UI.ITemplate.InstantiateIn

        End Sub
    End Class
#End Region
    <ToolboxData("<{0}:SearchGridView runat=server></{0}:SearchGridView>")> _
    <ParseChildren(True, "SearchFilters")> _
    Public Class SearchGridView
        Inherits GridView

<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;
	}
}