RasSetCredentials(vbNullString, sEntryName, rc, 0)返回为5求解决

--------------------编程问答-------------------- To set the default credentials for an all-user connection, set the RASCM_DefaultCreds flag in the dwMask member of the RASCREDENTIALS structure pointed to by the lpCredentials parameter. If you attempt to set default credentials for a per-user connection, RasSetCredentials returns ERROR_ACCESS_DENIED. 

好好看看上面的这段话，就是说不要设置dwMask的值中有RASCM_DefaultCreds（8）就可以了 --------------------编程问答--------------------  Dim rc As New RASCREDENTIALS
        With rc
            ReDim .szPassword(256)
            ReDim .szUserName(256)
            ReDim .szDomain(15)
            .dwSize = Marshal.SizeOf(rc)
            .dwMask = 3;//修改这里
 
            Dim bSrc(100) As Byte
            bSrc = System.Text.Encoding.ASCII.GetBytes(sUsername)
            Dim cbCopy As Integer = sUsername.Length()
            CopyMemory(.szUserName, bSrc, cbCopy)
            bSrc = System.Text.Encoding.ASCII.GetBytes(sPassword)
            cbCopy = sPassword.Length()
            CopyMemory(.szPassword, bSrc, cbCopy)
        End With

补充：VB ,  API