c#之序列化和反序列化 AjaxFileUploadEventArgs之未定义无参数构造函数'

我正在更改一个网络表单网站以使用 StateServer，现在我正试图找到一种方法来序列化和反序列化 AjaxFileUploadEventArgs，到目前为止我的代码:

在我的 html 中:

<ajaxToolkit:AjaxFileUpload 
ID="AAA" 
runat="server" 
OnUploadComplete="OnUploadComplete" 
ViewStateMode="Enabled" /> 

服务器:

protected void OnUploadComplete(object sender, AjaxFileUploadEventArgs file) 
        { 
            UpdateListInSession(file); 
        } 
 
public static void UpdateListInSession(AjaxFileUploadEventArgs file) 
{ 
  var serializer = new JavaScriptSerializer(); 
  var fileSerialized = serializer.Serialize(file); 
} 
 
public static AjaxFileUploadEventArgs GetLeadsListFromSession() 
{ 
    var serializer = new JavaScriptSerializer(); 
    AjaxFileUploadEventArgs file = null; 
 
    AjaxFileUploadEventArgs deserializeFile =  
         serializer.Deserialize<AjaxFileUploadEventArgs>( 
            HttpContext.Current.Session[k_file] as string); 
 
  return deserializeFile; 
} 

错误:

System.MissingMethodException: 'No parameterless constructor defined for type of 'AjaxControlToolkit.AjaxFileUploadEventArgs'.'

请您参考如下方法:

假设您使用的是 AjaxFileUploadEventArgs.cs来自 ajaxcontroltoolkit ，异常消息是不言自明的。您正在使用的序列化程序 JavaScriptSerializer 只能构造和反序列化具有无参数构造函数的类型，但如其 reference source 所示, AjaxFileUploadEventArgs 只有一个构造函数，它是参数化的:

public AjaxFileUploadEventArgs(string fileId, AjaxFileUploadState state, string statusMessage, string fileName, int fileSize, string contentType) { 
        // Initialize fields 
} 

那么，反序列化此类型的选项有哪些？首先，您可以切换到 json.net它支持开箱即用的参数化构造函数。安装 Json.NET 后，如果您这样做:

var deserializeFile =  
    Newtonsoft.Json.JsonConvert.DeserializeObject<AjaxFileUploadEventArgs>(jsonString); 

然后它就可以正常工作了。 sample fiddle .注意 Microsoft's own documentation对于 JavaScriptSerializer 状态:

Json.NET should be used serialization and deserialization.

所以这可能是最好的解决方案。

如果您出于某种原因不能使用 Json.NET，您将需要编写自定义 JavaScriptConverter AjaxFileUploadEventArgs 如下所示:

public class AjaxFileUploadEventArgsConverter : JavaScriptConverter 
{ 
    public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer) 
    { 
        var args = new AjaxFileUploadEventArgs 
        ( 
            serializer.ConvertItemToTypeOrDefault<string>(dictionary, "FileId"), 
            serializer.ConvertItemToTypeOrDefault<AjaxFileUploadState>(dictionary, "State"), 
            serializer.ConvertItemToTypeOrDefault<string>(dictionary, "StatusMessage"), 
            serializer.ConvertItemToTypeOrDefault<string>(dictionary, "FileName"), 
            serializer.ConvertItemToTypeOrDefault<int>(dictionary, "FileSize"),  
            serializer.ConvertItemToTypeOrDefault<string>(dictionary, "ContentType") 
        )  
        { PostedUrl = serializer.ConvertItemToTypeOrDefault<string>(dictionary, "PostedUrl") }; 
        return args; 
    } 
 
    public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer) 
    { 
        throw new NotImplementedException(); 
    } 
 
    public override IEnumerable<Type> SupportedTypes 
    { 
        get { return new[] { typeof(AjaxFileUploadEventArgs) }; } 
    } 
} 
 
public static class JavaScriptSerializerExtensions 
{ 
    public static T ConvertItemToTypeOrDefault<T>(this JavaScriptSerializer serializer, IDictionary<string, object> dictionary, string key) 
    { 
        object value; 
 
        if (!dictionary.TryGetValue(key, out value)) 
            return default(T); 
 
        return serializer.ConvertToType<T>(value); 
    } 
} 

然后反序列化如下:

var serializer = new JavaScriptSerializer(); 
serializer.RegisterConverters(new JavaScriptConverter[] { new AjaxFileUploadEventArgsConverter() }); 
var deserializeFile = serializer.Deserialize<AjaxFileUploadEventArgs>(jsonString);