异步自定义验证器方法

Question

我的 c# 项目中有一个自定义验证器，它将检查来自cloud firestore的重复 email ，但我意识到我的服务器端的异步方法导致自定义验证器不起作用，帮助....谢谢。

客户端：

<asp:CustomValidator ID="CustomValidatorEmail" ForeColor="Red" runat="server" ErrorMessage="Email already exits" ControlToValidate="txtEmail" OnServerValidate="CustomValidatorEmail_ServerValidate"></asp:CustomValidator>

服务器端：

 protected async void customValidatorEmail_ServerValidate(object source, ServerValidateEventArgs args)
{
            string enteredEmail = args.Value;

            Query query = database.Collection("Users");
            QuerySnapshot snap = await query.GetSnapshotAsync();

            foreach (DocumentSnapshot docsnap in snap) //retrieve everydata
            {
                GetAndSet retrieve = docsnap.ConvertTo<GetAndSet>();

                if (retrieve.Email.Equals(enteredEmail))
                {
                    args.IsValid = false;
                }
            }
        }