How to check active directory search result has particular property or not

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C#

Hello,
I am trying to get information from AD for a particular user. I wrote code for it but I am not sure if it's the right way to do the checking for mail property.

var user = new User();
var entry = new DirectoryEntry(LDAPservername, domainAndUsername, password);
var search = new DirectorySearcher(entry);
search.Filter = "(AccountName=" + userId + ")";
search.PropertiesToLoad.Add("cn");
search.PropertiesToLoad.Add("Name");
search.PropertiesToLoad.Add("mail");
search.PropertiesToLoad.Add("memberof");
SearchResult result;
try
{
result = search.FindOne();
}

Type t = result.GetType();
var p = t.GetProperty("mail");

if(p==null)
{
user.Email = "jhghjfajfjafjaf@gmail.com";
}

I want to check this result object has mail propertyName or not. If not then I want to assign a new value [

jhghjfajfjafjaf@gmail.com

] to it. Please take a look

What I have tried:

I tried this

Type t = result.GetType();
var p = t.GetProperty("mail");

if(p==null)
{
user.Email = "jhghjfajfjafjaf@gmail.com";
}