how to check the username in Active Directory in WPF - wpf

Question

I want to check whether username exists in Active Directory?
And depending on that I need to execute the code.
I have domain and username.How to check whether username exists in Active Directory without password using DirectorySearcher.

Answer 1

Your process has to be run under active directory user otherwise you should provide also active directory user credentials when creating PrincipalContext.
This is simple code to find user by userName:
var context = new PrincipalContext(ContextType.Domain, "yourDomainHost");
var userInfo = UserPrincipal.FindByIdentity(context, userName);
EDIT:
if you need to use directory searcher you can try this method:
bool ContainsUser(string domain, string userName)
{
string ldapBase = string.Format("LDAP://{0}", domain);
// in case if process is not running under AD user use: new DirectoryEntry(ldapBase, "userName", "password")
using (var entry = new DirectoryEntry(ldapBase))
{
using (var searcher = new DirectorySearcher(entry))
{
searcher.Filter = string.Format("(sAMAccountName={0})", userName);
return searcher.FindOne() != null;
}
}
}

Answer 2

You could try this approach:
DirectoryEntry entry = new DirectoryEntry("LDAP://DomainName");
DirectorySearcher dsearcher = new DirectorySearcher(entry);
dsearcher.Filter = "samaccountname=" + username;
SearchResult result = dsearcher.FindOne();
if(null!=result) //User Exists
{
//Do your stuff here
}
else //User Not Exists
{
//Do your stuff here
}
The above code assumes your AD Server is allowing anonymous access.