Delete an user in Active Directory via C#

I'm trying to delete an user in Active Directory via C#.When I attempt to run the following the code,I got an error.

Error Message:

A local error has occurred

Code:

DirectoryEntry ent = new DirectoryEntry("LDAP://192.168.1.99/OU=FIRMA");
    ent.Username = "idm\administrator";
    ent.Password = "123123QQ";
    DirectorySearcher dsrc = new DirectorySearcher(ent);
    dsrc.Filter = string.Format("(&(objectCategory=user)(SAMAccountName=adKullaniciadi))");
    DirectoryEntry silsunuya = ent.Children.Find("CN=adKullaniciadi","objectClass=person");
    ent.Children.Remove(silsunuya);
    ent.Close();
    silsunuya.Close();
    dsrc.Dispose();

I have an ASP.Net website running local that our IT team uses to delete AD accounts, and it seems to work ok. I remember when I was developing this application there were a lot of nuances I had to deal with, which can make it painful to figure out what's going on with AD. Here is the code I am using (in VB.Net):

Public Shared Function GetUser(ByVal username As String) As DirectoryEntry
    If String.IsNullOrEmpty(username) Then Return Nothing

    Dim path As String = ConfigurationManager.ConnectionStrings("ADConnectionString").ConnectionString
    Dim ds As New DirectorySearcher(path)

    ds.Filter = "(&(objectClass=user)(sAMAccountName=" + username + "))"
    ds.PropertiesToLoad.Add("sAMAccountName")         ' username
    ds.PropertiesToLoad.Add("mail")         ' e-mail address
    ds.PropertiesToLoad.Add("description")  ' Bureau ID
    ds.PropertiesToLoad.Add("company")      ' company name
    ds.PropertiesToLoad.Add("givenname")    ' first name
    ds.PropertiesToLoad.Add("sn")           ' last name
    ds.PropertiesToLoad.Add("name")         ' client name
    ds.PropertiesToLoad.Add("cn")           ' common name
    ds.PropertiesToLoad.Add("dn")           ' display name
    ds.PropertiesToLoad.Add("pwdLastSet")
    ds.SearchScope = SearchScope.Subtree
    Dim results As SearchResult = ds.FindOne

    If results IsNot Nothing Then
        Return New DirectoryEntry(results.Path)
    Else
        Return Nothing
    End If
End Function

Public Shared Sub DeleteUser(ByVal username As String, Optional ByVal useImpersonation As Boolean = False)
    Dim user As DirectoryEntry = GetUser(username)
    Dim ou As DirectoryEntry = user.Parent
    ou.Children.Remove(user)
    ou.CommitChanges()
End Sub

Looking at your code, here are some ideas that come to mind:

1. Try using dsrc.PropertiesToLoad.Add("sAMAccountName")
2. Try adding a call to ent.CommitChanges()
3. Can you verify the path and credentials are correct, say, using a command-line AD query tool?
4. Can you determine specifically what line the error occurs on?