Question

我将对象存储到Properties（如果尚未存储）：

if (!Application.Current.Properties.ContainsKey("user"))
{
    Application.Current.Properties.Add("user", user);
}

它存储了第一个对象。比我把它设置为null。当我尝试再次检查ContainsKey时，它会引发异常：

System.AggregateException: 'One or more errors occurred.'
SerializationException: Error in line 1 position 264. Element 'http://schemas.microsoft.com/2003/10/Serialization/Arrays:Value' contains data of the 'http://schemas.datacontract.org/2004/07/Layouts.Models:User' data contract. The deserializer has no knowledge of any type that maps to this contract. Add the type corresponding to 'User' to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding it to the list of known types passed to DataContractSerializer.

我应该删除......什么？

Answer 1

检查https://developer.xamarin.com/guides/xamarin-forms/application-fundamentals/application-class/处的文档：

注意：属性字典只能序列化基本类型存储。试图存储其他类型（例如List可以无声地失败。

在主题“持久性”中写道：“属性字典会自动保存到设备中。”因此，您会立即获得异常。

解决方法是手动序列化/反序列化User对象。以下是使用JSON序列化的示例：https://codemilltech.com/persist-whatever-you-want-with-xamarin-forms/

Answer 2

使用 Application.Current.Properties.Remove（ Key ）

Application.Current.Properties反序列化崩溃

2 个答案: