function UserLogin() {

        var username = $("#txtUsername").val();
        var passcode = $("#txtPassword").val();
        alert(username);

        $.ajax({

            url: '@Url.Action("Login", "UserAccount")',
            type: "POST",
            data: { 'username': username, 'passcode': passcode },
            datatype: "json",
            traditional: true,
            contentType: "application/json; charset=utf-8",
            success: function (data) {
                alert(data.username);

        }
    });

[HttpPost] public ActionResult Login(string username, string passcode) { if (IsValidUser(username, passcode)) { return RedirectToAction("UserInfo", "UserAccount"); } else { ModelState.AddModelError("", "Your Username or password is invalid"); } return View(); }

    private bool IsValidUser(string username, string passcode)
    {
        string Query = "Select Count(ID) from Users where Username ="   username   " and PassCode = "  passcode  "";
        int count = Convert.ToInt32(NpgSQLHelper.ExecuteScalar(Utility._connectionstring, System.Data.CommandType.Text, Query));
        if (count > 0)
        {
            return true;
        }
        else
        {
            return false;
        }
    }

CodePudding user response：

Remove the contentType: "application/json; charset=utf-8" or modify contentType to contentType:"application/x-www-form-urlencoded" can work fine.