ASP.NET

var username = WebSecurity.CurrentUserName; // the email field in database

// db is the DbContent variable, and someUserId can be the current user's id.

db.Users.FirstOrDefault(x => x.Id == someUserId);

// Fetch the data
var val = textBox1.Text; // your TextBox

// execute the SqlCommand; and get the value of reader (SqlDataReader) as bool for HasRows
if(hasRows) {
   // perform function for data_exists
} else {
   // nothing found in the database..
}

<script>
    var RedirectUrl = '<%=RedirectUrl%>';
    var HeadStart = '<%=HeadStart%>';
    var NewRole = '<%=NewRole%>';
    var GranteeId = '<%=GranteeId%>';
    var RoleTypeId = '<%=RoleTypeId%>'; 

    function RefreshParentWindow() {
        if ((HeadStart != null) && (HeadStart != undefined) && HeadStart && (HeadStart == "Y")) {
            if ((RedirectUrl != null) && (RedirectUrl != undefined) && RedirectUrl) {
                if (NewRole && (NewRole == "N")) {                    
                    parent.location.href = RedirectUrl;
                    parent.location.reload();
                }
            }
        }
    }
</script>

void btnSave_Click(object sender, EventArgs e)
        {
            using (StaffBusinessObject staffBO = new StaffBusinessObject(UserId, CurrentDate))
            {
                bool temp = Save(staffBO, true);

                if (temp && HeadStart == "Y" && NewRole == "Y")
                {
                    Response.Redirect(RedirectUrl);
                }
                else if (temp && HeadStart == "Y" && NewRole == "N")
                {
                    ScriptManager.RegisterStartupScript(this.Page, this.Page.GetType(), "script", "<script type='text/javascript'>RefreshParentWindow()();</script>", false);
                }
            }
        }