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I need to use a SOAP Extension within a .NET CF application. The
application invokes web services, and there is currently a
SoapHeaderAttribute specified for authentication information.

Within the web service proxy, there is a class defined like this:

[System.Xml.Serialization.XmlTypeAttribute(Namespac e="http://myurl")]

[System.Xml.Serialization.XmlRootAttribute(Namespac e="http://myurl",
IsNullable=false)]
public class MyAuthenticationHeader :
System.Web.Services.Protocols.SoapHeader {

/// <remarks/>
public string Username;

/// <remarks/>
public string Password;
}

The web method declaration within the web service proxy is currently:

[System.Web.Services.Protocols.SoapHeaderAttribute( "MyAuthenticationHeaderValue")]
[System.Web.Services.Protocols.SoapDocumentMethodAt tribute("http://myurl/MyWebMethod",
RequestNamespace="http://myurl", ResponseNamespace="http://myurl",
Use=System.Web.Services.Description.SoapBindingUse .Literal,
ParameterStyle=System.Web.Services.Protocols.SoapP arameterStyle.Wrapped)]
public string[] MyWebMethod(string[] arg1, string[] arg2) {
object[] results = this.Invoke("MyWebMethod", new object[]
{
arg1,
arg2});
return ((string[])(results[0]));
}


I want to add a SOAP Extension Attribute to the method declaration like
this:

[System.Web.Services.Protocols.SoapHeaderAttribute( "MyAuthenticationHeaderValue")]
[System.Web.Services.Protocols.SoapDocumentMethodAt tribute("http://myurl/MyWebMethod",
RequestNamespace="http://myurl", ResponseNamespace="http://myurl",
Use=System.Web.Services.Description.SoapBindingUse .Literal,
ParameterStyle=System.Web.Services.Protocols.SoapP arameterStyle.Wrapped)]
[MySoapExtension]
public string[] MyWebMethod(string[] arg1, string[] arg2) {
object[] results = this.Invoke("MyWebMethod", new object[]
{
arg1,
arg2});
return ((string[])(results[0]));
}

Everything works if I use EITHER the SoapHeaderAttribute OR the
SoapExtensionAttribute. However, if I try to use both, I get an
ArgumentNullException immediately after the GetInitializer() method in
my SOAP Extension class fires. There is no other information
available.

Worst case, I can put the authentication information into the SOAP
Header by means of my SOAP Extension, and just do without the
SoapHeaderAttribute. However, this is code someone else has written
and is maintaining, so I want to change it as little as possible.

Thanks in advance for any help.