Develop Reference

Is there a way to use <inheritdoc /> within a <list>?

I'm using XML tags to document my program so I can see descriptions when I hover over my classes, methods, and such. I want to display a list on one of my classes like so:
/// <remarks>
/// <b>List of methods below</b>
/// <list type="table">
/// <listheader>
/// <term>
/// <see cref="MyMethod()"/>
/// </term>
/// <description>
/// <inheritdoc cref="MyMethod()"/>
/// </description>
/// </listheader>
/// </list>
/// </remarks>
public class MyClass
{
/// <summary>
/// Description of MyMethod()
/// </summary>
public void MyMethod()
{
// Do something
}
}
The problem is that <inheritdoc /> is not loading anything in the preview. However, When I move <inheritdoc /> outside of the <list>, with the exact same formatting, it displays perfectly. Is there any way to reference the description of MyMethod() within the list?

<inheritdoc> by default includes all members in the target XML comments. If you need the <summary> you need to select it using the path attribute:
<inheritdoc cref="MyMethod" path='//summary/text()'/>
It should render something like this:

How to detect if system media player is playing music? [duplicate]

Using C# i'm trying to retrieve the name of the song that is currently playing and display it on a listBox, so every song that plays, it's shown in the listbox.
Using System;
Using WMPLib;
public IWMPMedia currentMedia { get; set; }
private void button1_Click(object sender, EventArgs e)
{
Player = new WMPLib.WindowsMediaPlayer();
string song = Player.currentMedia.name.ToString();
listBox1.Items.Add(song);
}
But it throws me the exception.
"Object reference not set to an instance of an object" here:
string song = Player.currentMedia.name.ToString();
Does anyone knows how to solve this?

You will have to use COM/OLE to do this. I did a program that did exactly that a little while ago, unfortunately tho I cannot find my client code, but I still have the code that implements IOleClientSite/IOleServiceProvider for WMPLib.
I found that code at the following URL:
http://sirayuki.sakura.ne.jp/WmpSample/WmpRemote.zip
Its some code that was writen by Jonathan Dibble, a Microsoft employee if I remember correctly. There is a CHM in the Zip with some explanation on each of the classes.
Heres the code that I still have, in case the link goes down, but like I said I cannot find my code that uses it. It worked almost correctly but I remember that one of the bug left was that it would leave behind wmplayer.exe processes after the media player and my application were closed.
UPDATE!
found some client code and a slighlty modified version of RemotedWindowsMediaPlayer.cs
I just found some coded that I tested this with, and it works. Its from a Winform project, and you need to reference WMPLib for this to work.
In my form I added a button and this code:
/// <summary>
/// Default Constructor
/// </summary>
RemotedWindowsMediaPlayer rm;
public FrmMain()
{
//
// Required for Windows Form Designer support
//
InitializeComponent();
//Call me old fashioned - I like to do this stuff manually. You can do a drag
//drop if you like, it won't change the results.
rm = new RemotedWindowsMediaPlayer();
rm.Dock = System.Windows.Forms.DockStyle.Top;
panel1.Controls.Add(rm);
return;
}
private void button1_Click(object sender, EventArgs e)
{
MessageBox.Show(((WMPLib.IWMPPlayer4)rm.GetOcx()).currentMedia.sourceURL);
}
RemotedWindowsMediaPLayer.cs:
namespace RemoteWMP
{
using System;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using WMPLib;
/// <summary>
/// This is the actual Windows Media Control.
/// </summary>
[System.Windows.Forms.AxHost.ClsidAttribute("{6bf52a52-394a-11d3-b153-00c04f79faa6}")]
[ComVisible(true)]
[ClassInterface(ClassInterfaceType.AutoDispatch)]
public class RemotedWindowsMediaPlayer : System.Windows.Forms.AxHost,
IOleServiceProvider,
IOleClientSite
{
/// <summary>
/// Used to attach the appropriate interface to Windows Media Player.
/// In here, we call SetClientSite on the WMP Control, passing it
/// the dotNet container (this instance.)
/// </summary>
protected override void AttachInterfaces()
{
try
{
//Get the IOleObject for Windows Media Player.
IOleObject oleObject = this.GetOcx() as IOleObject;
if (oleObject != null)
{
//Set the Client Site for the WMP control.
oleObject.SetClientSite(this as IOleClientSite);
// Try and get the OCX as a WMP player
if (this.GetOcx() as IWMPPlayer4 == null)
{
throw new Exception(string.Format("OCX is not an IWMPPlayer4! GetType returns '{0}'",
this.GetOcx().GetType()));
}
}
else
{
throw new Exception("Failed to get WMP OCX as an IOleObject?!");
}
return;
}
catch (System.Exception ex)
{
System.Diagnostics.Debug.WriteLine(ex.ToString());
}
}
#region IOleServiceProvider Memebers - Working
/// <summary>
/// During SetClientSite, WMP calls this function to get the pointer to <see cref="RemoteHostInfo"/>.
/// </summary>
/// <param name="guidService">See MSDN for more information - we do not use this parameter.</param>
/// <param name="riid">The Guid of the desired service to be returned. For this application it will always match
/// the Guid of <see cref="IWMPRemoteMediaServices"/>.</param>
/// <returns></returns>
IntPtr IOleServiceProvider.QueryService(ref Guid guidService, ref Guid riid)
{
//If we get to here, it means Media Player is requesting our IWMPRemoteMediaServices interface
if (riid == new Guid("cbb92747-741f-44fe-ab5b-f1a48f3b2a59"))
{
IWMPRemoteMediaServices iwmp = new RemoteHostInfo();
return Marshal.GetComInterfaceForObject(iwmp, typeof(IWMPRemoteMediaServices));
}
throw new System.Runtime.InteropServices.COMException("No Interface", (int) HResults.E_NOINTERFACE);
}
#endregion
#region IOleClientSite Members
/// <summary>
/// Not in use. See MSDN for details.
/// </summary>
/// <exception cref="System.Runtime.InteropServices.COMException">E_NOTIMPL</exception>
void IOleClientSite.SaveObject()
{
throw new System.Runtime.InteropServices.COMException("Not Implemented", (int) HResults.E_NOTIMPL);
}
/// <summary>
/// Not in use. See MSDN for details.
/// </summary>
/// <exception cref="System.Runtime.InteropServices.COMException"></exception>
object IOleClientSite.GetMoniker(uint dwAssign, uint dwWhichMoniker)
{
throw new System.Runtime.InteropServices.COMException("Not Implemented", (int) HResults.E_NOTIMPL);
}
/// <summary>
/// Not in use. See MSDN for details.
/// </summary>
/// <exception cref="System.Runtime.InteropServices.COMException"></exception>
object IOleClientSite.GetContainer()
{
return (int)HResults.E_NOINTERFACE;
}
/// <summary>
/// Not in use. See MSDN for details.
/// </summary>
/// <exception cref="System.Runtime.InteropServices.COMException"></exception>
void IOleClientSite.ShowObject()
{
throw new System.Runtime.InteropServices.COMException("Not Implemented", (int) HResults.E_NOTIMPL);
}
/// <summary>
/// Not in use. See MSDN for details.
/// </summary>
/// <exception cref="System.Runtime.InteropServices.COMException"></exception>
void IOleClientSite.OnShowWindow(bool fShow)
{
throw new System.Runtime.InteropServices.COMException("Not Implemented", (int) HResults.E_NOTIMPL);
}
/// <summary>
/// Not in use. See MSDN for details.
/// </summary>
/// <exception cref="System.Runtime.InteropServices.COMException"></exception>
void IOleClientSite.RequestNewObjectLayout()
{
throw new System.Runtime.InteropServices.COMException("Not Implemented", (int) HResults.E_NOTIMPL);
}
#endregion
/// <summary>
/// Default Constructor.
/// </summary>
public RemotedWindowsMediaPlayer() :
base("6bf52a52-394a-11d3-b153-00c04f79faa6")
{
}
}
}
RemoteHostInfo.cs
using System;
namespace RemoteWMP
{
using System.Runtime.InteropServices;
/// <summary>
/// This class contains the information to return to Media Player about our remote service.
/// </summary>
[ComVisible(true)]
[ClassInterface(ClassInterfaceType.None)]
public class RemoteHostInfo :
IWMPRemoteMediaServices
{
#region IWMPRemoteMediaServices Members
/// <summary>
/// Returns "Remote" to tell media player that we want to remote the WMP application.
/// </summary>
/// <returns></returns>
public string GetServiceType()
{
return "Remote";
}
/// <summary>
/// The Application Name to show in Windows Media Player switch to menu
/// </summary>
/// <returns></returns>
public string GetApplicationName()
{
return System.Diagnostics.Process.GetCurrentProcess().ProcessName;
}
/// <summary>
/// Not in use, see MSDN for more info.
/// </summary>
/// <param name="name"></param>
/// <param name="dispatch"></param>
/// <returns></returns>
public HResults GetScriptableObject(out string name, out object dispatch)
{
name = null;
dispatch = null;
//return (int) HResults.S_OK;//NotImplemented
return HResults.E_NOTIMPL;
}
/// <summary>
/// For skins, not in use, see MSDN for more info.
/// </summary>
/// <param name="file"></param>
/// <returns></returns>
public HResults GetCustomUIMode(out string file)
{
file = null;
return HResults.E_NOTIMPL;//NotImplemented
}
#endregion
}
}
COM Interfaces.cs
using System;
namespace RemoteWMP
{
using System.Runtime.InteropServices;
#region Useful COM Enums
/// <summary>
/// Represents a collection of frequently used HRESULT values.
/// You may add more HRESULT VALUES, I've only included the ones used
/// in this project.
/// </summary>
public enum HResults
{
/// <summary>
/// HRESULT S_OK
/// </summary>
S_OK = unchecked((int)0x00000000),
/// <summary>
/// HRESULT S_FALSE
/// </summary>
S_FALSE = unchecked((int)0x00000001),
/// <summary>
/// HRESULT E_NOINTERFACE
/// </summary>
E_NOINTERFACE = unchecked((int)0x80004002),
/// <summary>
/// HRESULT E_NOTIMPL
/// </summary>
E_NOTIMPL = unchecked((int)0x80004001),
/// <summary>
/// USED CLICKED CANCEL AT SAVE PROMPT
/// </summary>
OLE_E_PROMPTSAVECANCELLED = unchecked((int)0x8004000C),
}
/// <summary>
/// Enumeration for <see cref="IOleObject.GetMiscStatus"/>
/// </summary>
public enum DVASPECT
{
/// <summary>
/// See MSDN for more information.
/// </summary>
Content = 1,
/// <summary>
/// See MSDN for more information.
/// </summary>
Thumbnail = 2,
/// <summary>
/// See MSDN for more information.
/// </summary>
Icon = 3,
/// <summary>
/// See MSDN for more information.
/// </summary>
DocPrint = 4
}
/// <summary>
/// Emumeration for <see cref="IOleObject.Close"/>
/// </summary>
public enum TAGOLECLOSE :uint{
OLECLOSE_SAVEIFDIRTY = unchecked((int)0),
OLECLOSE_NOSAVE = unchecked((int)1),
OLECLOSE_PROMPTSAVE = unchecked((int)2)
}
#endregion
#region IWMPRemoteMediaServices
/// <summary>
/// Interface used by Media Player to determine WMP Remoting status.
/// </summary>
[ComImport,
ComVisible(true),
InterfaceType(ComInterfaceType.InterfaceIsIUnknown),
Guid("CBB92747-741F-44fe-AB5B-F1A48F3B2A59")]
public interface IWMPRemoteMediaServices
{
/// <summary>
/// Service type.
/// </summary>
/// <returns><code>Remote</code> if the control is to be remoted (attached to WMP.)
/// <code>Local</code>if this is an independent WMP instance not connected to WMP application. If you want local, you shouldn't bother
/// using this control!
/// </returns>
[return: MarshalAs(UnmanagedType.BStr)]
string GetServiceType();
/// <summary>
/// Value to display in Windows Media Player Switch To Application menu option (under View.)
/// </summary>
/// <returns></returns>
[return: MarshalAs(UnmanagedType.BStr)]
string GetApplicationName();
/// <summary>
/// Not in use, see MSDN for details.
/// </summary>
/// <param name="name"></param>
/// <param name="dispatch"></param>
/// <returns></returns>
[PreserveSig]
[return: MarshalAs(UnmanagedType.U4)]
HResults GetScriptableObject([MarshalAs(UnmanagedType.BStr)] out string name,
[MarshalAs(UnmanagedType.IDispatch)] out object dispatch);
/// <summary>
/// Not in use, see MSDN for details.
/// </summary>
/// <param name="file"></param>
/// <returns></returns>
[PreserveSig]
[return: MarshalAs(UnmanagedType.U4)]
HResults GetCustomUIMode([MarshalAs(UnmanagedType.BStr)] out string file);
}
#endregion
#region IOleServiceProvider
/// <summary>
/// Interface used by Windows Media Player to return an instance of IWMPRemoteMediaServices.
/// </summary>
[ComImport,
GuidAttribute("6d5140c1-7436-11ce-8034-00aa006009fa"),
InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown),
ComVisible(true)]
public interface IOleServiceProvider
{
/// <summary>
/// Similar to QueryInterface, riid will contain the Guid of an object to return.
/// In our project we will look for <see cref="IWMPRemoteMediaServices"/> Guid and return the object
/// that implements that interface.
/// </summary>
/// <param name="guidService"></param>
/// <param name="riid">The Guid of the desired Service to provide.</param>
/// <returns>A pointer to the interface requested by the Guid.</returns>
IntPtr QueryService(ref Guid guidService, ref Guid riid);
}
/// <summary>
/// This is an example of an INCORRECT entry - do not use, unless you want your app to break.
/// </summary>
[ComImport,
GuidAttribute("6d5140c1-7436-11ce-8034-00aa006009fa"),
InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown),
ComVisible(true)]
public interface BadIOleServiceProvider
{
/// <summary>
/// This is incorrect because it causes our return interface to be boxed
/// as an object and a COM callee may not get the correct pointer.
/// </summary>
/// <param name="guidService"></param>
/// <param name="riid"></param>
/// <returns></returns>
/// <example>
/// For an example of a correct definition, look at <see cref="IOleServiceProvider"/>.
/// </example>
[return: MarshalAs(UnmanagedType.Interface)]
object QueryService(ref Guid guidService, ref Guid riid);
}
#endregion
#region IOleClientSite
/// <summary>
/// Need to implement this interface so we can pass it to <see cref="IOleObject.SetClientSite"/>.
/// All functions return E_NOTIMPL. We don't need to actually implement anything to get
/// the remoting to work.
/// </summary>
[ComImport,
ComVisible(true),
Guid("00000118-0000-0000-C000-000000000046"),
InterfaceType(ComInterfaceType.InterfaceIsIUnknown) ]
public interface IOleClientSite
{
/// <summary>
/// See MSDN for more information. Throws <see cref="COMException"/> with id of E_NOTIMPL.
/// </summary>
/// <exception cref="COMException">E_NOTIMPL</exception>
void SaveObject();
/// <summary>
/// See MSDN for more information. Throws <see cref="COMException"/> with id of E_NOTIMPL.
/// </summary>
/// <exception cref="COMException">E_NOTIMPL</exception>
[return: MarshalAs(UnmanagedType.Interface)]
object GetMoniker(uint dwAssign, uint dwWhichMoniker);
/// <summary>
/// See MSDN for more information. Throws <see cref="COMException"/> with id of E_NOTIMPL.
/// </summary>
/// <exception cref="COMException">E_NOTIMPL</exception>
[return: MarshalAs(UnmanagedType.Interface)]
object GetContainer();
/// <summary>
/// See MSDN for more information. Throws <see cref="COMException"/> with id of E_NOTIMPL.
/// </summary>
/// <exception cref="COMException">E_NOTIMPL</exception>
void ShowObject();
/// <summary>
/// See MSDN for more information. Throws <see cref="COMException"/> with id of E_NOTIMPL.
/// </summary>
/// <exception cref="COMException">E_NOTIMPL</exception>
void OnShowWindow(bool fShow);
/// <summary>
/// See MSDN for more information. Throws <see cref="COMException"/> with id of E_NOTIMPL.
/// </summary>
/// <exception cref="COMException">E_NOTIMPL</exception>
void RequestNewObjectLayout();
}
#endregion
#region IOleObject
/// <summary>
/// This interface is implemented by WMP ActiveX/COM control.
/// The only function we need is <see cref="SetClientSite"/>.
/// </summary>
[ComImport, ComVisible(true),
Guid("00000112-0000-0000-C000-000000000046"),
InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IOleObject
{
/// <summary>
/// Used to pass our custom <see cref="IOleClientSite"/> object to WMP. The object we pass must also
/// implement <see cref="IOleServiceProvider"/> to work right.
/// </summary>
/// <param name="pClientSite">The <see cref="IOleClientSite"/> to pass.</param>
void SetClientSite(IOleClientSite pClientSite);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
[return: MarshalAs(UnmanagedType.Interface)]
IOleClientSite GetClientSite();
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
void SetHostNames(
[MarshalAs(UnmanagedType.LPWStr)]string szContainerApp,
[MarshalAs(UnmanagedType.LPWStr)]string szContainerObj);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
void Close(uint dwSaveOption);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
void SetMoniker(uint dwWhichMoniker, object pmk);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
[return: MarshalAs(UnmanagedType.Interface)]
object GetMoniker(uint dwAssign, uint dwWhichMoniker);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
void InitFromData(object pDataObject, bool fCreation, uint dwReserved);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
object GetClipboardData(uint dwReserved);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
void DoVerb(uint iVerb, uint lpmsg, [MarshalAs(UnmanagedType.Interface)]object pActiveSite,
uint lindex, uint hwndParent, uint lprcPosRect);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
[return: MarshalAs(UnmanagedType.Interface)]
object EnumVerbs();
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
void Update();
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
[PreserveSig]
[return: MarshalAs(UnmanagedType.U4)]
HResults IsUpToDate();
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
Guid GetUserClassID();
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
[return: MarshalAs(UnmanagedType.LPWStr)]
string GetUserType(uint dwFormOfType);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
void SetExtent(uint dwDrawAspect, [MarshalAs(UnmanagedType.Interface)] object psizel);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
[return: MarshalAs(UnmanagedType.Interface)]
object GetExtent(uint dwDrawAspect);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
uint Advise([MarshalAs(UnmanagedType.Interface)]object pAdvSink);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
void Unadvise(uint dwConnection);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
[return: MarshalAs(UnmanagedType.Interface)]
object EnumAdvise();
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
uint GetMiscStatus([MarshalAs(UnmanagedType.U4)] DVASPECT dwAspect);
/// <summary>
/// Implemented by Windows Media Player ActiveX control.
/// See MSDN for more information.
/// </summary>
void SetColorScheme([MarshalAs(UnmanagedType.Interface)] object pLogpal);
}
#endregion
}

Converter file section is null

I'm making a BRRES to BFRES converter. For some reason, the MDL0 section seems to be always null when debugging. Here is the code for the Brres file loader:
/// <summary>
/// Represents a set of properties controlling the load of a <see cref="Brres.BrresFile"/>.
/// </summary>
internal class BrresLoaderContext
{
// ---- CONSTRUCTORS -------------------------------------------------------------------------------------------
/// <summary>
/// Initializes a new instance of the <see cref="BrresLoaderContext"/> class for the given <see cref="BrresFile"/>
/// instance using the given <see cref="BinaryDataReader"/>.
/// </summary>
/// <param name="BrresFile">The <see cref="BrresFile"/> instance to load the data in.</param>
/// <param name="reader">The <see cref="BinaryDataReader"/> to use for reading the data.</param>
internal BrresLoaderContext(BrresFile brresFile, BinaryDataReader reader)
{
BrresFile = brresFile;
Reader = reader;
Warnings = new List<string>();
}
// ---- PROPERTIES ---------------------------------------------------------------------------------------------
/// <summary>
/// Gets the <see cref="BrresFile"/> instance which is loaded to.
/// </summary>
internal BrresFile BrresFile
{
get;
private set;
}
/// <summary>
/// Gets the <see cref="BinaryDataReader"/> which is used to read data from the input stream.
/// </summary>
internal BinaryDataReader Reader
{
get;
private set;
}
/// <summary>
/// Gets or sets the warnings raised after loading the Brres file.
/// </summary>
internal List<string> Warnings
{
get;
private set;
}
}
I mostly didn't update comments.
So why is it null?

XML Comments - How do you reference a dictionary indexer properly?

As the name states, I have no idea how to reference a dictionary indexer. Any help here? :)
FYI, I've tried:
<see cref="Item"/>
<see cref="Item(Int32)"/> //Highly doubted this would work.
<see cref="Item(TKey)"/>
<see cref="Item[TKey]"/>

You can use the full property syntax to reference indexers:
namespace ConsoleApplication1
{
/// <summary>
/// See indexer <see cref="P:ConsoleApplication1.MyDictionary`2.Item(`0)"/>
/// </summary>
/// <typeparam name="TKey"></typeparam>
/// <typeparam name="TValue"></typeparam>
public class MyDictionary<TKey, TValue>
{
/// <summary>
/// Indexer
/// </summary>
/// <param name="key"></param>
/// <returns></returns>
public TValue this[TKey key]
{
get { return default(TValue); }
set { }
}
}
}
You can check that the property was resolved properly by inspecting the generated XML file:
<doc>
<assembly>
<name>ConsoleApplication1</name>
</assembly>
<members>
<member name="T:ConsoleApplication1.MyDictionary`2">
<summary>
See <see cref="P:ConsoleApplication1.MyDictionary`2.Item(`0)"/>
</summary>
<typeparam name="TKey"></typeparam>
<typeparam name="TValue"></typeparam>
</member>
<member name="P:ConsoleApplication1.MyDictionary`2.Item(`0)">
<summary>
Indexer
</summary>
<param name="key"></param>
<returns></returns>
</member>
</members>
</doc>
Notice how the first P: matches the second one.
Finally, make sure it's working with Intellisense:
Update by Original Poster (myermian):
I did a little bit of digging and have discovered that the shortform of an indexer property is just "this". Ex: <see cref="this"/>

Try <see cref="P:Item(System.Int32)" /> (the name is Item, not Items)

Convert List<T> to object[]

I am looking for a one liner that transforms List<T> into object[]. It's one liner, so I am not interested in solutions such as foreach, or for...
Any takers?
Hint: No, both List<T>.ToArray() and List<T>.ToArray<object>() don't work.
Edit: Why List<T>.ToArray<object>() doesn't work? Because it can't compile.

mylist.Cast<object>().ToArray()
That will only iterate once, by the way, in case you were wondering about the performance. O(n). :)
Why? Well, because Cast<object> will use deferred execution and won't actually do anything until the list is iterated by ToArray().

List<T>.Select(x => x as object).ToArray();
Should return an object[].

If you don't have Linq (.Net 3.0) then you can use the ConvertAll() and ToArray() methods in List:
List<T> list = new List<T>();
object[] objects = list.ConvertAll<object>(item => (object)item).ToArray();

theList.Cast<object>().ToArray()
or
new List<object>(theList).ToArray()

And for a pre-LINQ solution (that only works for reference types).
(object[])List<T>.ToArray();

If you don't mind writing a very short, reusable function, the ConvertAll Extension Method might help:
http://msdn.microsoft.com/en-us/library/73fe8cwf.aspx
EDIT:
This would work too
List<int> intList = new List<int>() { 1, 3, 4 };
object[] objectList = intList.ConvertAll(item => (object)item).ToArray();

In C# on .NET 2.0 (VS 2008) the following compiles and doesn't use LINQ (as far as I can see) for reference types.
object[] oArray;
List<MyObject> oList = new List<MyObject>();
oArray = oList.ToArray();
This does not require a cast as all reference types have object as their base.

I'd suggest creating a ListCastAdapter,
Lets say you want to Convert List to List
Create implementation of
an implementation of IList that return items from a List
most likely i call it class ListCastAdapter
Have a great day
implementation (NOT TESTED):
Notice: It is recomended to make the list ReadOnly,
for the fact, now the user can insert objects that are way up the hierarchy in the original
list.
Note: CopyTo() is not implemented, you can create the same idea for the array.
using System.Collections;
using System.Collections.Generic;
namespace UDF.MyDataLayer
{
internal class ListCastAdapter<S,T> : IList<T> where T : class where S : class
{
private List<S> adaptee;
public ListCastAdapter(List<S> adaptee )
{
this.adaptee = adaptee;
}
#region Implementation of IEnumerable
public class EnumeratorCastAdapter : IEnumerator<T>
{
private IEnumerator<S> adaptee;
public EnumeratorCastAdapter(IEnumerator<S> adaptee)
{
this.adaptee = adaptee;
}
#region Implementation of IDisposable
/// <summary>
/// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
/// </summary>
/// <filterpriority>2</filterpriority>
public void Dispose()
{
adaptee.Dispose();
}
#endregion
#region Implementation of IEnumerator
/// <summary>
/// Advances the enumerator to the next element of the collection.
/// </summary>
/// <returns>
/// true if the enumerator was successfully advanced to the next element; false if the enumerator has passed the end of the collection.
/// </returns>
/// <exception cref="T:System.InvalidOperationException">The collection was modified after the enumerator was created. </exception><filterpriority>2</filterpriority>
public bool MoveNext()
{
return adaptee.MoveNext();
}
/// <summary>
/// Sets the enumerator to its initial position, which is before the first element in the collection.
/// </summary>
/// <exception cref="T:System.InvalidOperationException">The collection was modified after the enumerator was created. </exception><filterpriority>2</filterpriority>
public void Reset()
{
adaptee.Reset();
}
/// <summary>
/// Gets the element in the collection at the current position of the enumerator.
/// </summary>
/// <returns>
/// The element in the collection at the current position of the enumerator.
/// </returns>
public T Current
{
get
{
// needs to check if it is an Object or Value Type
return adaptee.Current as T;
}
}
/// <summary>
/// Gets the current element in the collection.
/// </summary>
/// <returns>
/// The current element in the collection.
/// </returns>
/// <exception cref="T:System.InvalidOperationException">The enumerator is positioned before the first element of the collection or after the last element.</exception><filterpriority>2</filterpriority>
object IEnumerator.Current
{
get { return Current; }
}
#endregion
}
/// <summary>
/// Returns an enumerator that iterates through the collection.
/// </summary>
/// <returns>
/// A <see cref="T:System.Collections.Generic.IEnumerator`1"/> that can be used to iterate through the collection.
/// </returns>
/// <filterpriority>1</filterpriority>
public IEnumerator<T> GetEnumerator()
{
return new EnumeratorCastAdapter(adaptee.GetEnumerator());
}
/// <summary>
/// Returns an enumerator that iterates through a collection.
/// </summary>
/// <returns>
/// An <see cref="T:System.Collections.IEnumerator"/> object that can be used to iterate through the collection.
/// </returns>
/// <filterpriority>2</filterpriority>
IEnumerator IEnumerable.GetEnumerator()
{
return adaptee.GetEnumerator();
}
#endregion
#region Implementation of ICollection<T>
/// <summary>
/// Adds an item to the <see cref="T:System.Collections.Generic.ICollection`1"/>.
/// </summary>
/// <param name="item">The object to add to the <see cref="T:System.Collections.Generic.ICollection`1"/>.</param><exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.ICollection`1"/> is read-only.</exception>
public void Add(T item)
{
adaptee.Add(item as S);
}
/// <summary>
/// Removes all items from the <see cref="T:System.Collections.Generic.ICollection`1"/>.
/// </summary>
/// <exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.ICollection`1"/> is read-only. </exception>
public void Clear()
{
adaptee.Clear();
}
/// <summary>
/// Determines whether the <see cref="T:System.Collections.Generic.ICollection`1"/> contains a specific value.
/// </summary>
/// <returns>
/// true if <paramref name="item"/> is found in the <see cref="T:System.Collections.Generic.ICollection`1"/>; otherwise, false.
/// </returns>
/// <param name="item">The object to locate in the <see cref="T:System.Collections.Generic.ICollection`1"/>.</param>
public bool Contains(T item)
{
return adaptee.Contains(item as S);
}
/// <summary>
/// Copies the elements of the <see cref="T:System.Collections.Generic.ICollection`1"/> to an <see cref="T:System.Array"/>, starting at a particular <see cref="T:System.Array"/> index.
/// </summary>
/// <param name="array">The one-dimensional <see cref="T:System.Array"/> that is the destination of the elements copied from <see cref="T:System.Collections.Generic.ICollection`1"/>. The <see cref="T:System.Array"/> must have zero-based indexing.</param><param name="arrayIndex">The zero-based index in <paramref name="array"/> at which copying begins.</param><exception cref="T:System.ArgumentNullException"><paramref name="array"/> is null.</exception><exception cref="T:System.ArgumentOutOfRangeException"><paramref name="arrayIndex"/> is less than 0.</exception><exception cref="T:System.ArgumentException"><paramref name="array"/> is multidimensional.-or-The number of elements in the source <see cref="T:System.Collections.Generic.ICollection`1"/> is greater than the available space from <paramref name="arrayIndex"/> to the end of the destination <paramref name="array"/>.-or-Type <paramref name="T"/> cannot be cast automatically to the type of the destination <paramref name="array"/>.</exception>
public void CopyTo(T[] array, int arrayIndex)
{
throw new System.NotImplementedException("Not Needed by Me, implement ArrayCastAdapter if needed");
}
/// <summary>
/// Removes the first occurrence of a specific object from the <see cref="T:System.Collections.Generic.ICollection`1"/>.
/// </summary>
/// <returns>
/// true if <paramref name="item"/> was successfully removed from the <see cref="T:System.Collections.Generic.ICollection`1"/>; otherwise, false. This method also returns false if <paramref name="item"/> is not found in the original <see cref="T:System.Collections.Generic.ICollection`1"/>.
/// </returns>
/// <param name="item">The object to remove from the <see cref="T:System.Collections.Generic.ICollection`1"/>.</param><exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.ICollection`1"/> is read-only.</exception>
public bool Remove(T item)
{
adaptee.Remove(item as S);
}
/// <summary>
/// Gets the number of elements contained in the <see cref="T:System.Collections.Generic.ICollection`1"/>.
/// </summary>
/// <returns>
/// The number of elements contained in the <see cref="T:System.Collections.Generic.ICollection`1"/>.
/// </returns>
public int Count
{
get { return adaptee.Count; }
}
/// <summary>
/// Gets a value indicating whether the <see cref="T:System.Collections.Generic.ICollection`1"/> is read-only.
/// </summary>
/// <returns>
/// true if the <see cref="T:System.Collections.Generic.ICollection`1"/> is read-only; otherwise, false.
/// </returns>
public bool IsReadOnly
{
get
{
return true; // change, to live on the edge
}
}
#endregion
#region Implementation of IList<T>
/// <summary>
/// Determines the index of a specific item in the <see cref="T:System.Collections.Generic.IList`1"/>.
/// </summary>
/// <returns>
/// The index of <paramref name="item"/> if found in the list; otherwise, -1.
/// </returns>
/// <param name="item">The object to locate in the <see cref="T:System.Collections.Generic.IList`1"/>.</param>
public int IndexOf(T item)
{
return adaptee.IndexOf(item as S);
}
/// <summary>
/// Inserts an item to the <see cref="T:System.Collections.Generic.IList`1"/> at the specified index.
/// </summary>
/// <param name="index">The zero-based index at which <paramref name="item"/> should be inserted.</param><param name="item">The object to insert into the <see cref="T:System.Collections.Generic.IList`1"/>.</param><exception cref="T:System.ArgumentOutOfRangeException"><paramref name="index"/> is not a valid index in the <see cref="T:System.Collections.Generic.IList`1"/>.</exception><exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.IList`1"/> is read-only.</exception>
public void Insert(int index, T item)
{
adaptee.Insert(index, item as S);
}
/// <summary>
/// Removes the <see cref="T:System.Collections.Generic.IList`1"/> item at the specified index.
/// </summary>
/// <param name="index">The zero-based index of the item to remove.</param><exception cref="T:System.ArgumentOutOfRangeException"><paramref name="index"/> is not a valid index in the <see cref="T:System.Collections.Generic.IList`1"/>.</exception><exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.IList`1"/> is read-only.</exception>
public void RemoveAt(int index)
{
adaptee.RemoveAt(index);
}
/// <summary>
/// Gets or sets the element at the specified index.
/// </summary>
/// <returns>
/// The element at the specified index.
/// </returns>
/// <param name="index">The zero-based index of the element to get or set.</param><exception cref="T:System.ArgumentOutOfRangeException"><paramref name="index"/> is not a valid index in the <see cref="T:System.Collections.Generic.IList`1"/>.</exception><exception cref="T:System.NotSupportedException">The property is set and the <see cref="T:System.Collections.Generic.IList`1"/> is read-only.</exception>
public T this[int index]
{
get { return adaptee[index] as T; }
set { adaptee[index] = value as S; }
}
#endregion
}
}