Lock and Unlock the application state in asp.net

Add this on your ASPX design page

        <asp:Label ID="Label1" runat="server" Font-Size="Larger" ForeColor="Green">
        </asp:Label>
        <br />
        <br />
        <asp:Button ID="Button1" runat="server" Text="Click Me" OnClick="Button1_Click"
            Font-Bold="true" ForeColor="Red" />

Add this on your C# page

    protected void Button1_Click(object sender, System.EventArgs e)
    {
        Application.Lock();

        int clickMeCounter = 0;
        if (Application["clickMeCounter"] != null)
        {
            clickMeCounter = (int)Application["clickMeCounter"];
        }
        clickMeCounter++;
        Application["clickMeCounter"] = clickMeCounter;
        Application.UnLock();

        Label1.Text = "Button Clicked: " + clickMeCounter.ToString() + " times";
    }