How do I get the full domain name in VB.NET

[Gajendra1]

I want a common sign on solution developed in VB.NET for my company's software. For this I require the full domain name of the server. But my problem is that I don't have any idea about how to do so. Someone suggested me to use Environ("USERDNSDOMAIN"), but since I am not an expert in VB.NET I need your guidance on how to use it. Below is my code:

Public Class MyForm Inherits System.Web.UI.Page

#MyCode "My Generated Code"

    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
    End Sub

    Protected WithEvents txtDomain As System.Web.UI.WebControls.TextBox
    Protected WithEvents lblName As System.Web.UI.WebControls.Label
    Protected WithEvents btnRefresh As System.Web.UI.WebControls.Button
   
    Private designerPlaceholderDeclaration As System.Object

    Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init
        InitializeComponent()
    End Sub

#End MyCode 

    Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        txtDomain.Text = "Test"
    End Sub

    Private Sub btnRefresh_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnRefresh.Click
        txtDomain.Text = System.Environment.GetEnvironmentVariable("USERDNSDOMAIN")
    End Sub

End Class

[CitricAcid]

You missed out to add system.management reference.

Imports System.Management

Module MyModule 

    Sub Main()
        Using objSearch As New ManagementObjectSearcher(New SelectQuery("Win32_ComputerSystem"))
            For Each mngtObj As ManagementObject In searcher.[Get]()
                Dim myDomainName As String = String.Format("{0}.{1}", mngtObj("name"), If(CBool(mngtObj("partofdomain")), mngtObj("domain"), mngtObj("workgroup")))
                Console.WriteLine(myDomainName)
                Exit For
            Next
        End Using

    End Sub

End Module

[fellah]

A better idea would be:

Public Function GetCompInfo() As Boolean

        Dim objSearch As ManagementObjectSearcher
        Dim objCollection As ManagementObjectCollection
        Dim sqlCommand As String = "SELECT * FROM Win32_ComputerSystem"
        Dim mngtScope As ManagementScope = New ManagementScope("root\cimv2")
        Dim newQuery As SelectQuery = New SelectQuery(sqlCommand)

        objSearch = New ManagementObjectSearcher(mngtScope, newQuery)
        objCollection = objSearch.Get()

        Dim mngtObject As ManagementObject

        For Each management_object In objCollection 
            Console.WriteLine(mngtObject("Domain") + "\" + mngtObject("Name"))
        Next mngtObject 

        Return True
    End Function

[Gajendra1]

Thank you for your suggestions. I tried all that changing it based on my software. CitricAcid, I am unable to let my Visual Studio understand the using function but always I end up with build error. However I tried something different as below:

Private Function myDomainName()
    Dim ipHost as System.Net.IPHostEntry = System.Net.Dns.Resolve("SERVER")
    Dim domainName As String = ipHost.hostname
    Return domainName 
End Function

[!const]

Here is a slight modification to your code which is required according to me:

Dim getHostName As String = System.Net.Dns.GetHostName

Private Function myDomainName()
    Dim getHostName As String = System.Net.Dns.GetHostName
    Dim ipHost as System.Net.IPHostEntry = System.Net.Dns.Resolve(getHostName)
    Dim domainName As String = ipHost.hostname
    Return domainName 
End Function