如何使用out参数调用方法？

Question

我想暴露WebClient.DownloadDataInternal方法，如下所示：

[ComVisible(true)]
public class MyWebClient : WebClient
{
    private MethodInfo _DownloadDataInternal;

    public MyWebClient()
    {
        _DownloadDataInternal = typeof(WebClient).GetMethod("DownloadDataInternal", BindingFlags.NonPublic | BindingFlags.Instance);
    }

    public byte[] DownloadDataInternal(Uri address, out WebRequest request)
    {
        _DownloadDataInternal.Invoke(this, new object[] { address, out request });
    }

}

WebClient.DownloadDataInternal有一个out参数，我不知道如何调用它。 救命！

Answer 1

您可以像通过任何其他方法一样通过反射调用带有out参数的方法。 不同之处在于返回的值将被复制回参数数组，以便您可以从调用函数访问它。

object[] args = new object[] { address, request };
_DownloadDataInternal.Invoke(this, args);
request = (WebRequest)args[1];

Answer 2

public class MyWebClient : WebClient
{
    delegate byte[] DownloadDataInternal(Uri address, out WebRequest request);

    DownloadDataInternal downloadDataInternal;

    public MyWebClient()
    {
        downloadDataInternal = (DownloadDataInternal)Delegate.CreateDelegate(
            typeof(DownloadDataInternal),
            this,
            typeof(WebClient).GetMethod(
                "DownloadDataInternal",
                BindingFlags.NonPublic | BindingFlags.Instance));
    }

    public byte[] DownloadDataInternal(Uri address, out WebRequest request)
    {
        return downloadDataInternal(address, out request);
    }
}