PAG blocks

I've been having some trouble with a few Microsoft Application blocks lately, mainly threading issues. Haven't spent too much time on it yet, but they don't seems to be fully thread safe. Well the PAG group is taking the existing PAG blocks and developing them into the Microsoft Enterprise Library (http://www.gotdotnet.com/community/workspaces/workspace.aspx?ID=295A464A-6072-4E25-94E2-91BE63527327) I hope they've taken threading into considerations.

BITS C# Wrapper

I was recently using BITS (Background Intelligent Transfer Service) to create a component for uploading and downloading files asynchronously from a windows sharepoint services document library. One of the requirement was transfer can only be done by authenticated users. BITS version 1.5 and above supports this via the IBackgroundCopyJob2::SetCredentials method. However, this method uses an union in its parameter and C# does not have union. After playing with interop attributes for a while I've worked out the necessary attributes to make this work with a C# only wrapper without going to managed C++.

After looking at the definition for BG_AUTH_CREDENTIALS in the .h file from the SDK, it turns out that the union (BG_AUTH_CREDENTIALS_UNION) only contains one type which is BG_BASIC_CREDENTIALS. I was able to make the call to SetCredentials work by using the FieldOffset attribute in the struct definitions.

Here is an extract of the important struct definitions.

internal enum BG_AUTH_SCHEME
{
// Fields
BG_AUTH_SCHEME_BASIC = 1,
BG_AUTH_SCHEME_DIGEST = 2,
BG_AUTH_SCHEME_NTLM = 3,
BG_AUTH_SCHEME_NEGOTIATE = 4,
BG_AUTH_SCHEME_PASSPORT = 5
}

internal enum BG_AUTH_TARGET
{
// Fields
BG_AUTH_TARGET_SERVER = 1,
BG_AUTH_TARGET_PROXY = 2,
}

[StructLayout(LayoutKind.Explicit, Size=16, Pack=4)]
internal struct BG_AUTH_CREDENTIALS
{
[FieldOffset(0)]
public BG_AUTH_TARGET Target;

[FieldOffset(4)]
public BG_AUTH_SCHEME Scheme;

[FieldOffset(8)]
public BG_AUTH_CREDENTIALS_UNION Credentials;
}

[StructLayout(LayoutKind.Explicit, Size=8, Pack=4)]
internal struct BG_AUTH_CREDENTIALS_UNION
{
[FieldOffset(0)]
public BG_BASIC_CREDENTIALS Basic;
}

[StructLayout(LayoutKind.Explicit, Size=8, Pack=4)]
internal struct BG_BASIC_CREDENTIALS
{
[FieldOffset(0)]
[MarshalAs(UnmanagedType.LPWStr)]
public string UserName;

[FieldOffset(4)]
[MarshalAs(UnmanagedType.LPWStr)]
public string Password;
}

I've posted the interop library at http://www.gotdotnet.com/Community/UserSamples/Details.aspx?SampleGuid=99f2f473-26de-41cd-bf39-8f7e75fda5aa

Start my blog

Well I think it is time to start my own blog, so here is my first entry.