PRB: "System.InvalidOperationException" Error While Serializing NameValueCollection Objects Using XmlSerializer (814187)


The information in this article applies to:

  • Microsoft Visual Basic .NET (2003)
  • Microsoft Visual Basic .NET (2002)
  • Microsoft Visual C# .NET (2003)
  • Microsoft Visual C# .NET (2002)
  • Microsoft XML Classes (included with the .NET Framework 1.0)
  • Microsoft XML Classes (included with the .NET Framework 1.1)

Beta Information

This article discusses a Beta release of a Microsoft product. The information in this article is provided as-is and is subject to change without notice.

No formal product support is available from Microsoft for this Beta product. For information about how to obtain support for a Beta release, see the documentation that is included with the Beta product files, or check the Web location from which you downloaded the release.

SYMPTOMS

When you try to serialize NameValueCollection objects by using the XMLSerializer object, you receive the following exception error message:
An unhandled exception of type 'System.InvalidOperationException' occurred in system.xml.dll
Additional information: You must implement the Add(System.String) method on System.Collections.Specialized.NameValueCollection because it inherits from ICollection.

CAUSE

NameValueCollection does not directly implement the ICollection interface. Instead, NameValueCollection extends NameObjectCollectionBase. This implements the ICollection interface, and the overloaded Add(system.string) method is not implemented in the NameValueCollection class. When you use the XMLSerializer, the XmlSerializer tries to serialize or deserialize the NameValueCollection as a generic ICollection. Therefore, it looks for the default Add(System.String). In the absence of the Add(system.String) method, the exception is thrown.

WORKAROUND

To work around this problem, use the SoapFormatter class for serialization instead of using XML Serialization.

Note To use the SoapFormatter class, you must add a reference to System.Runtime.Serialization.Formatters.Soap.dll.

Visual C# .NET Code


The following code describes using the SOAPFormatter in Visual C# .NET:
using System;
using System.IO;
using System.Xml;
using System.Xml.Serialization;
using System.Collections.Specialized;
using System.Runtime.Serialization.Formatters.Soap;

namespace MyConsoleApplication
{
	class Class1
	{
		[STAThread]
		static void Main(string[] args)
		{
			// Defining a NameValueCollection object
			NameValueCollection namValColl = new NameValueCollection();
			// Adding some sample data to NameValueCollection Object
			namValColl.Add("name1", "value1");
						
			// Serializing NameValueCollection object by using SoapFormatter
			SoapFormatter sf = new SoapFormatter();
			Stream strm1 = File.Open(@"C:\datasoap.xml", FileMode.OpenOrCreate,FileAccess.ReadWrite);
			sf.Serialize(strm1,namValColl);
			strm1.Close();
			// End of SOAP Serialization
			
			// Deserializing the XML file into NameValueCollection object
			// by using SoapFormatter
			SoapFormatter sf1 = new SoapFormatter();
			Stream strm2 = File.Open(@"C:\datasoap.xml", FileMode.Open,FileAccess.Read);
			NameValueCollection namValColl1 = (NameValueCollection)sf1.Deserialize(strm2);
			strm2.Close();
			// End of SOAP Deserialization
		}
	}
}

Visual Basic .NET Code


The following code describes using the SoapFormatter in Visual Basic .NET:
Imports System
Imports System.IO
Imports System.Xml.Serialization
Imports System.Collections.Specialized
Imports System.Runtime.Serialization.Formatters.Soap

Module Module1

   Sub Main()
      ' Defining a NameValueCollection object
      Dim namValColl As New NameValueCollection()
      ' Adding some sample data to NameValueCollection Object
      namValColl.Add("name1", "value1")

      ' Serializing NameValueCollection object by using SoapFormatter
      Dim sf As SoapFormatter = New SoapFormatter()
      Dim strm1 As Stream = File.Open("C:\datasoapvb.xml", FileMode.OpenOrCreate, FileAccess.ReadWrite)
      sf.Serialize(strm1, namValColl)
      strm1.Close()
      ' End of SOAP Serialization

      ' Deserializing the XML file into NameValueCollection object
      ' by using SoapFormatter
      Dim sf1 As SoapFormatter = New SoapFormatter()
      Dim strm2 As Stream = File.Open("C:\datasoapvb.xml", FileMode.Open, FileAccess.Read)
      Dim namValColl1 As NameValueCollection = sf1.Deserialize(strm2)
      strm2.Close()
      ' End of SOAP Deserialization
   End Sub

End Module

STATUS

This behavior is by design.

MORE INFORMATION

Steps to Reproduce the Behavior

  1. Start Microsoft Visual Studio .NET.
  2. On the File menu, point to New, and then click Project.
  3. Under Project Types, click Visual C# Projects or Visual Basic Projects, and then click Console Application under Templates.
  4. Name the project MyConsoleApplication, and then click OK.
  5. Replace the existing code with the following code:

    Visual C# .NET Code

    using System;
using System.IO;
using System.Xml.Serialization ;
using System.Collections.Specialized;

namespace MyConsoleApplication
{
	class Class1
	{
	
		[STAThread]
		static void Main(string[] args)
		{
			// Defining a NameValueCollection object.
			NameValueCollection namValColl = new NameValueCollection();
			// Adding some sample data to NameValueCollection Object
			namValColl.Add("name1", "value1");
			
			// Serializing the NameValueCollection object using XMLSerializer
			XmlSerializer mySerializer = new XmlSerializer(typeof(NameValueCollection));
			Stream strm1 = File.Open(@"C:\datasoap.xml", FileMode.OpenOrCreate,FileAccess.ReadWrite);
			mySerializer.Serialize(strm1, namValColl);
			strm1.Close();
		}
	}
}

    Using Visual Basic .NET Code

    Imports System
Imports System.IO
Imports System.Xml.Serialization
Imports System.Collections.Specialized
Module Module1

  Sub Main()
      ' Defining a NameValueCollection object.
      Dim namValColl As New NameValueCollection
      ' Adding some sample data to NameValueCollection Object
      namValColl.Add("name1", "value1")
        
      ' Serializing the NameValueCollection object using XMLSerializer
      Dim mySerializer As New XmlSerializer(GetType(NameValueCollection))
      Dim strm1 As Stream
      strm1 = File.Open("C:\datasoap.xml", FileMode.OpenOrCreate, FileAccess.ReadWrite)
      mySerializer.Serialize(strm1, namValColl)
      strm1.Close()
  End Sub

End Module
  6. On the Debug menu, click Start. You receive the exception error message that is described in the "Symptoms" section of this article.

REFERENCES

For additional information, click the following article numbers to view the articles in the Microsoft Knowledge Base:

323503 WebCast: XML Serialization and Sample Code

314150 INFO: Roadmap for XML Serialization in the .NET Framework


Modification Type:MajorLast Reviewed:9/24/2003
Keywords:kberrmsg kbSerial kbCollections kbCollectionClass kbprb KB814187 kbAudDeveloper
©2003 Microsoft Corporation. All rights reserved.