从系统剪贴板获取自定义数据时出现COMException [英] COMException when getting custom data from system clipboard
问题描述
我在C#代码中定义了一个自定义类型FooNode.我想将该自定义类型的实例添加到全局System.Windows.Forms.Clipboard，然后再次从剪贴板中检索它.该添加似乎有效，但是我无法检索该实例.检索后，一些异常会打印到标准输出，如下所示:
I have a custom type, FooNode, defined in my C# code. I want to add an instance of that custom type to the global System.Windows.Forms.Clipboard, and then retrieve it from the clipboard again. The add seems to work, but I am not able to retrieve the instance. Upon retrieval, several exceptions print to standard output like the following:
A first chance exception of type ''System.Runtime.InteropServices.COMException'' occurred in System.Windows.Forms.dll<br />(... and 9 more just like above)
检索结果为空引用.没有崩溃或停止.上述例外情况正在内部处理；我无法抓住他们.问题不在于DataObject本身，因为我可以从中检索FooNode.我只是无法从剪贴板的DataObject中获取我的FooNode.
我能够向系统剪贴板中添加其他类型的对象，然后将它们放到其中，例如字符串和System.Guid.为什么无法检索自定义类型的对象?
以下是我的测试代码.调用FooTest.Test()运行.
The result of the retrieval is a null reference. There is no crash or halt. The above exceptions are being dealt with internally; I am not able to catch them. The problem is not with the DataObject itself, because I can retrieve my FooNode from it. I just can''t retreive my FooNode from the clipboard''s DataObject.
I am able to add and then retreive other types of objects to the system clipboard, such as strings and System.Guid. Why can I not retrieve an object of my custom type?
Following is my test code. Call FooTest.Test() to run.
using System;
using System.Diagnostics;
using System.Windows.Forms;
public class FooNode
{
private Guid m_Guid;
private string m_Name = String.Empty;
public FooNode( )
{
m_Guid = Guid.NewGuid();
m_Name = "Foo";
}
public Guid Guid
{
get { return m_Guid; }
set { m_Guid = value; }
}
public string Name
{
get { return m_Name; }
set { m_Name = value; }
}
}
public class FooTest
{
// Entry point for test of using system clipboard.
public static void Test( )
{
FooNode fooNode = new FooNode();
// Add a FooNode to the system clipboard.
DataObject dob = new DataObject( fooNode );
dob.SetData( typeof( Guid ), fooNode.Guid );
dob.SetData( DataFormats.StringFormat, fooNode.Guid.ToString() );
Clipboard.SetDataObject( dob );
// Retrieve the FooNode from the system clipboard.
// *** Notice that the returned object is null. ***
object raw = Clipboard.GetDataObject().GetData( typeof( FooNode ) );
// Demonstrate what can and cannot be retrieved from the clipboard.
Spam( Clipboard.GetDataObject(), new Type[] { typeof( FooNode ), typeof( Guid ) } );
}
public static void Spam( IDataObject dob, Type[] types )
{
Debug.WriteLine( dob );
Debug.Indent();
Debug.WriteLine( "Data formats:" );
Debug.Indent();
string[] formatNames = dob.GetFormats( true );
foreach ( string name in formatNames )
{
Debug.WriteLine( name );
}
Debug.Unindent();
// Test if I can access the data by format name.
foreach ( string name in formatNames )
{
if ( dob.GetDataPresent( name ) )
{
Debug.WriteLine( String.Format( "Present as format=\"{0}\"", name ) );
Debug.Indent();
object raw = dob.GetData( name );
Debug.WriteLine( String.Format( "raw={0}", raw != null ? raw : "null" ) );
Debug.Unindent();
}
}
// Test if I can access the data by type.
if ( types != null )
{
foreach ( Type type in types )
{
if ( dob.GetDataPresent( type ) )
{
Debug.WriteLine( String.Format( "Present as type={0}", type ) );
Debug.Indent();
object raw = dob.GetData( type );
Debug.WriteLine( String.Format( "raw={0}", raw != null ? raw : "null" ) );
Debug.Unindent();
}
}
}
Debug.Unindent();
}
}
推荐答案
I 在这件事上我不是专家，但我怀疑您的对象是否可以放入剪贴板.我有一个预感，您的FooNode类需要一个[可序列化].另外，您可能想在Clipboard.SetDataObject()中添加，true"，以使对象在应用程序中生存.
:)
Hi,
I''m no expert in this matter, but I doubt your object makes it to the Clipboard. I have a hunch you need a [Serializable] for your FooNode class. Also you may want to add ",true" to Clipboard.SetDataObject() to make your object survive your app.
:)
这篇关于从系统剪贴板获取自定义数据时出现COMException的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
