Question

出于单元测试的目的，我想创建一个SqlCeLockTimeoutException

类型的模拟对象

由于它的构造函数受到保护，我在测试中创建了一个扩展类：

[Serializable]
private class TestableSqlCeLockTimeoutException : SqlCeLockTimeoutException
{
    public TestableSqlCeLockTimeoutException()
           : this(new SerializationInfo(typeof (TestableSqlCeLockTimeoutException), 
                                        new FormatterConverter()), 
                  new StreamingContext())
    {
    }

    protected TestableSqlCeLockTimeoutException(SerializationInfo info,
                                                StreamingContext context) 
           : base(info, context)
    {
    }
}

但是，在创建实例时，我不断收到以下异常：

测试方法 Foo 引发异常：
System.Runtime.Serialization.SerializationException：Member＆＃39; ClassName＆＃39;没找到。

为什么我一直这样做？我尝试使用Serializable属性无效。

任何解决方法都会有所帮助。

Answer 1

@Mugan你问过一个非常有趣的问题！为了回答这个问题，我不得不反编译SqlCeLockTimeoutException。当我试图帮助你时，我学到了很多东西。谢谢。

问题发生因为System.Exception C`tor需要反序列化一些属性：

[System.Security.SecuritySafeCritical]  // auto-generated
protected Exception(SerializationInfo info, StreamingContext context) 
{
 //some validation
    _className = info.GetString("ClassName");
    _message = info.GetString("Message");
    _data = (IDictionary)(info.GetValueNoThrow("Data",typeof(IDictionary)));
    _innerException = (Exception)(info.GetValue("InnerException",typeof(Exception)));
    _helpURL = info.GetString("HelpURL");
    _stackTraceString = info.GetString("StackTraceString");
    _remoteStackTraceString = info.GetString("RemoteStackTraceString");
    _remoteStackIndex = info.GetInt32("RemoteStackIndex");
    _exceptionMethodString = (String)(info.GetValue("ExceptionMethod",typeof(String)));
    HResult = info.GetInt32("HResult");
    _source = info.GetString("Source");
//some bla bla....

为了解决上述问题，我将受保护的C`tor更改为public，然后使用它：

var info = new SerializationInfo(typeof (TestableSqlCeLockTimeoutException), 
           new FormatterConverter());
info.AddValue("ClassName", string.Empty);
info.AddValue("Message", string.Empty);
info.AddValue("InnerException", new ArgumentException());
info.AddValue("HelpURL", string.Empty);
info.AddValue("StackTraceString", string.Empty);
info.AddValue("RemoteStackTraceString", string.Empty);
info.AddValue("RemoteStackIndex", 0);
info.AddValue("ExceptionMethod", string.Empty);
info.AddValue("HResult", 1);
info.AddValue("Source", string.Empty);
new TestableSqlCeLockTimeoutException(info,new StreamingContext());

然后这次从SqlCeException引发了新的异常。 SqlCeException Ctor还需要一个属性__Errors__：

protected SqlCeException(SerializationInfo info, StreamingContext context)
  : base(info, context)
{
  if (info == null)
    throw new ArgumentNullException("info");
  this.Errors = (SqlCeErrorCollection) info.GetValue("__Errors__", typeof (SqlCeErrorCollection));
}

SqlCeErrorCollection Ctor是内部的，因此我使用Reflaction创建了一个实例：

BindingFlags flags = BindingFlags.NonPublic | BindingFlags.Instance;
CultureInfo culture = null; // use InvariantCulture or other if you prefer
object instantiatedType =
       Activator.CreateInstance(typeof(SqlCeErrorCollection), flags, null, null, culture);
info.AddValue("__Errors__", instantiatedType);

现在每件事都有效。我最终得到了一种创作方法：

private static SqlCeLockTimeoutException CreateSqlCeLockTimeoutExceptionForTest()
{
    var info = new SerializationInfo(typeof (TestableSqlCeLockTimeoutException), 
               new FormatterConverter());
    info.AddValue("ClassName", string.Empty);
    info.AddValue("Message", string.Empty);
    info.AddValue("InnerException", new ArgumentException());
    info.AddValue("HelpURL", string.Empty);
    info.AddValue("StackTraceString", string.Empty);
    info.AddValue("RemoteStackTraceString", string.Empty);
    info.AddValue("RemoteStackIndex", 0);
    info.AddValue("ExceptionMethod", string.Empty);
    info.AddValue("HResult", 1);
    info.AddValue("Source", string.Empty);
    BindingFlags flags = BindingFlags.NonPublic | BindingFlags.Instance;
    CultureInfo culture = null; // use InvariantCulture or other if you prefer
    object instantiatedType = Activator.CreateInstance(typeof (SqlCeErrorCollection), 
                                flags, null, null, culture);
    info.AddValue("__Errors__", instantiatedType);
    return new TestableSqlCeLockTimeoutException(info, new StreamingContext());
}

您还可以使用Reflaction创建SqlCeLockTimeoutException的新实例，而不是TestableSqlCeLockTimeoutException：

private static SqlCeLockTimeoutException CreateSqlCeLockTimeoutExceptionForTest()
{
    BindingFlags flags = BindingFlags.NonPublic | BindingFlags.Instance;
    CultureInfo culture = null; // use InvariantCulture or other if you prefer
    object instantiatedType = Activator.CreateInstance(typeof (SqlCeErrorCollection), 
                  flags, null, null, culture);

    object result = Activator.CreateInstance(typeof(SqlCeLockTimeoutException), 
                  flags, null, new []{instantiatedType}, culture);

    return (SqlCeLockTimeoutException)result;
}

创建SqlCeLockTimeoutException的实例

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