How to rectify the issue "invalid viewstate" while doing csrf token validation in ASP.NET with C#?

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C#

ASP.NET

I am doing csrf token validation in asp.net with c#.
I am sending the cookie as a separate header.
I am getting the exception of Invalid view state while doing the same.
My core code is updated as below

What I have tried:

Code is as below:

 var requestCookie = Request.Cookies[AntiXsrfTokenKey];
                Guid requestCookieGuidValue;
                if (requestCookie != null && TryParseGuid(requestCookie.Value, out requestCookieGuidValue))
                {
                   
                    // Use the Anti-XSRF token from the cookie
                    _antiXsrfTokenValue = requestCookie.Value;
                   
                    Page.ViewStateUserKey = _antiXsrfTokenValue;
                   
                }
                else
                {
                    
                    _antiXsrfTokenValue = Guid.NewGuid().ToString("N");
                   Page.ViewStateUserKey = _antiXsrfTokenValue;
                    /for setting AntiXSRF Token Value as a separate header XSRFHeader instead in theresponse header Start
                    //Response.Cookies.Set(responseCookie);
                     Response.AppendHeader("XSRFHeader", _antiXsrfTokenValue);
                  }
                    
 Page.PreLoad += csrf_Page_PreLoad;

protected void csrf_Page_PreLoad(object sender, EventArgs e)
        {
            try
            {
                Common.WriteDDSLog("csrf_Page_PreLoad Started ...............");
                if (!IsPostBack)
                {
                    // Set Anti-XSRF token
                   
                    ViewState[AntiXsrfTokenKey] = Page.ViewStateUserKey;
                    ViewState[AntiXsrfUserNameKey] = Context.User.Identity.Name ?? String.Empty;
                    
                }
                else
                {
                    
                    // Validate the Anti-XSRF token
                    if ((string)ViewState[AntiXsrfTokenKey] != _antiXsrfTokenValue
                        || (string)ViewState[AntiXsrfUserNameKey] != (Context.User.Identity.Name ?? String.Empty))
                    {
                        Common.WriteDDSLog("Validation of Anti-XSRF token failed in csrf_Page_PreLoad");
                        Response.Redirect("~/CustomError.aspx", false);

                    }
                   
                }

            }
            catch (Exception ex)
            {
                
        }

        #endregion Code for adding anti-csrf token