What is the use of := in this program? [duplicate]

Question

Possible Duplicate:
VB.NET := Operator

Yesterday I was browsing through Microsoft® Agent code snippets and I saw := used while calling a function.

I tried searching it in Google but I could not find anything related to it.

Is := used because we are calling a function of COM Library ?

Code :

Public Class Form1

    Dim agent As AgentObjects.Agent
    Dim merlin As AgentObjects.IAgentCtlCharacter

    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        agent.Characters.Unload("merlin")
        merlin = Nothing
        agent = Nothing
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        agent = New AgentObjects.Agent
        agent.Connected = True
        agent.Characters.Load(CharacterID:="Merlin", LoadKey:="merlin.acs")
        merlin = agent.Characters(CharacterID:="Merlin")
        agent.PropertySheet.Visible = True
    End Sub

    Public Sub IntroMerlin()
        Dim strName As String
        With merlin
            'Display character.
            .Show()
            'Make the character play an animation.
            .Play(Animation:="Greet")
            .Play(Animation:="Restpose")
            .Speak(Text:="Hello!")
            .Play(Animation:="Announce")
            .Speak(Text:="I am Merlin.")
            .Play(Animation:="Pleased")
            .Speak(Text:="It is nice to meet you.")
        End With
    End Sub
End Class

Thanks.

Answer 1

Those are named parameters. It can be especially handy if a function has a long list of parameters with defaults. You just name the ones you want to provide values for, and you don't have to deal with positional requirements.

Answer 2

This is how you specify "named arguments" in VB/VBA/VB.NET -- providing arguments by their name instead of their position. See, for example, this blog post.