如何使用JSON字符串表示法传递作为另一个对象成员的对象

我有这个类:

public class TAccount
{
    public Account account { set; get; }
    public double transactionAmount { set; get; }
}

这个类:

public class Account
{
    public int Id { set; get; }
    public string AccountName { set; get; }
    public double Balance { set; get; }
    public string LastOperation { set; get; }
}

我想发布以下jsonstring，但它看不到，我试图添加值到帐户对象内的TAccount类

jsonstring:

{ "TransactionAmount": 98, "Account":[{"Id" : 4 , "LastOperation" : "credit"}]}

public class TAccount
{
    public Account account { get; set; }
    public double transactionAmount { get; set; }
}

public class Account
{
    public int Id { get; set; }
    public string AccountName { get; set; }
    public double Balance { get; set; }
    public string LastOperation { get; set; }
}

{
    "transactionAmount": 98,
    "account": {
        "Id": 4,
        "LastOperation": "credit"
    }
}