C# Signature:

[DllImport("ole32.dll")]
static extern int CoInitializeSecurity(IntPtr pVoid, int cAuthSvc,
   SOLE_AUTHENTICATION_SERVICE [] asAuthSvc, IntPtr pReserved1,
   uint dwAuthnLevel, uint dwImpLevel, IntPtr pAuthList, uint dwCapabilities,
   IntPtr pReserved3);

VB .NET Signature:

Declare Function CoInitializeSecurity Lib "ole32.dll" (pVoid As IntPtr, _
   cAuthSvc As Integer, asAuthSvc() As SOLE_AUTHENTICATION_SERVICE, _
   pReserved1 As IntPtr, dwAuthnLevel As Integer, dwImpLevel As Integer, _
   pAuthList As IntPtr, dwCapabilities As Integer, pReserved3 As IntPtr) As Integer

User-Defined Types:

SOLE_AUTHENTICATION_SERVICE

Notes:

You shouldn't call CoInitializeSecurity from managed code. That's because the CLR will almost always call CoInitialize upon startup before execution enters your main method, and CoInitialize will implicitly call CoInitializeSecurity if it hasn't already been called. Therefore, calling this from managed code will usually return RPC_E_TOO_LATE.

The workaround is to write an unmanaged "shim" that will call CoInitializeSecurity, then activate and call into managed code. You can do this via an export from a mixed-mode C++ DLL, by registering a managed component for use by COM, or by using the CLR hosting API.

You can prevent the CLR from calling CoInitializeEx and CoInitializeSecurity automatically on startup, by removing the STAThread or MTAThread attribute from above Main(). You can then explicitly call CoInitializeEx/CoInitializeSecurity with any specific authentication settings you require.

Alternative Managed API:

Do you know one? Please contribute it!