如何将类型_ComObject转换为本机类型，如Long或其他（获得强制转换错误）？

Posted 2021-04-21

我试图通过调用从Active Directory获取LastLogonTimestamp

Principal.ExtensionGet("lastLogonTimestamp")

VB.NET代码：

<DirectoryProperty("lastLogonTimestamp")>
Public Property LastLogonTimestamp() As Date? ' no matter what this type is, I cannot cast the Object coming in
    Get
        Dim valueArray = ExtensionGet("lastLogonTimestamp")
        If valueArray Is Nothing OrElse valueArray.Length = 0 Then Return Nothing
        Return DateTime.FromFileTimeUtc(valueArray(0))
    End Get
    Set(value As Date?)
        ExtensionSet("lastLogonTimestamp", value)
    End Set
End Property

这将返回Object（即Object()）或null的数组。麻烦的是它抱怨我的演员对Long（或其他类型我尝试过：ULong，Date和String）。它总是告诉我这样的事情：

从类型'_ComObject'到类型'Long'的转换无效。

在a new question，我开始走另一条路（从DateTime到64位）

答案

通过下面的HansPassant评论使用link中提供的C＃代码，我使用以下VB代码解决了这个问题：

<DirectoryProperty("lastLogonTimestamp")>
Public Property LastLogonTimestamp() As Date?
    Get
        'Dim valueArray = GetProperty("whenChanged")
        Dim valueArray = ExtensionGet("lastLogonTimestamp") 'ExtensionGet("LastLogon")
        If valueArray Is Nothing OrElse valueArray.Length = 0 Then Return Nothing

        Dim lastLogonDate = valueArray(0)
        Dim lastLogonDateType = lastLogonDate.GetType()
        Dim highPart = CType(lastLogonDateType.InvokeMember("HighPart", Reflection.BindingFlags.GetProperty, Nothing, lastLogonDate, Nothing), Int32)
        Dim lowPart = CType(lastLogonDateType.InvokeMember("LowPart", Reflection.BindingFlags.GetProperty Or Reflection.BindingFlags.Public, Nothing, lastLogonDate, Nothing), Int32)
        Dim longDate = CLng(highPart) << 32 Or (CLng(lowPart) And &HFFFFFFFFL)
        Dim result = IIf(longDate > 0, CType(DateTime.FromFileTime(longDate), DateTime?), Nothing)

        Return result
        'Return DateTime.FromFileTimeUtc(valueArray(0))
    End Get
    Set(value As Date?)
        ExtensionSet("lastLogonTimestamp", value)
    End Set
End Property

而C＃版本（剪辑自source）：

[DirectoryProperty("RealLastLogon")]
public DateTime? RealLastLogon
{
    get
    {
        if (ExtensionGet("LastLogon").Length > 0)
        {
            var lastLogonDate = ExtensionGet("LastLogon")[0];
            var lastLogonDateType = lastLogonDate.GetType();
            var highPart = (Int32)lastLogonDateType.InvokeMember("HighPart", BindingFlags.GetProperty, null, lastLogonDate, null);
            var lowPart = (Int32)lastLogonDateType.InvokeMember("LowPart", BindingFlags.GetProperty | BindingFlags.Public, null, lastLogonDate, null);

            var longDate = ((Int64)highPart << 32 | (UInt32)lowPart);

            return longDate > 0 ? (DateTime?) DateTime.FromFileTime(longDate) : null;
        }

        return null;
    }
}