Detect Browser Refresh Avoid Events Fire In ASP.NET

Detect Browser Refresh In Asp.Net 2.0,3.5,4.0 To Avoid Events Getting Fired Or Event Firing,If you are inserting some data in database in Click event of button, After click if user refresh the page than click event gets fired again resulting data insertion to database again.

To stop event fire on browser refresh we need to write bit of code.

In this example i've put a Label and a Button on the page, on click the label Text becomes Hello and when i refresh the page label's text again becomes Hello

HTML SOURCE

---

   1:  <asp:Label ID="Label1" runat="server" Text=""/>

   2:   

   3:  <asp:Button ID="Button1" runat="server" 

   4:              OnClick="Button1_Click" Text="Button"/>

In Page_Load event i m creating a Session Variable and assigning System date and time to it , and in Page_Prerender event i am creating a Viewstate variable and assigning Session variable's value to it.

Than in button's click event i am checking the values of Session variable and Viewstate variable if they both are equal than page is not refreshed otherwise it has been refreshed

C# CODE

---

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            Session["CheckRefresh"] =
            Server.UrlDecode(System.DateTime.Now.ToString());
        }
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        if (Session["CheckRefresh"].ToString() == ViewState["CheckRefresh"].ToString())
        {
            Label1.Text = "Hello";
            Session["CheckRefresh"] =
            Server.UrlDecode(System.DateTime.Now.ToString());
        }
        else
        {
            Label1.Text = "Page Refreshed";
        }
    }

    protected void Page_PreRender(object sender, EventArgs e)
    {
        ViewState["CheckRefresh"] = Session["CheckRefresh"];
    }

VB.NET

---

Protected Sub Page_Load(sender As Object, e As EventArgs)
 If Not IsPostBack Then
  Session("CheckRefresh") = Server.UrlDecode(System.DateTime.Now.ToString())
 End If
End Sub
Protected Sub Button1_Click(sender As Object, e As EventArgs)
 If Session("CheckRefresh").ToString() = ViewState("CheckRefresh").ToString() Then
  Label1.Text = "Hello"
  Session("CheckRefresh") = Server.UrlDecode(System.DateTime.Now.ToString())
 Else
  Label1.Text = "Page Refreshed"
 End If
End Sub

Protected Sub Page_PreRender(sender As Object, e As EventArgs)
 ViewState("CheckRefresh") = Session("CheckRefresh")
End Sub