Checking an array for duplicate before inserting a new value

Question

Hi all I have an array that contains email addresses before inserting a new address which are being read from a text file into the array how can I check that the address doesn't already exist in the array? I'm trying to make sure there are no duplicates in the array rather than sorting the array once they are all in can I check before inserting the address? Many thanks PS Using .net 2.0 J

Satish Kathi · Answer

Here is code for using array List ArrayList email = new ArrayList (); if (!email.Contains(your email string read from file)) { email.Add(your email string read from file); } If you are using dictionary Dictionary string  string > email2 = new Dictionary string  string >(); if (!email2.ContainsKey(your email string read from file)) { email2.Add(your email string read from file your email string read from file); } Dictionary is a collection of key value pair. Key must be unique. Retrieving the value is very fast as it is implemented as a hash table.

Niradhip Chakraborty · Answer

ArrayList EmailAddresses=new ArrayList(); Dictionary dictionary = new Dictionary (); foreach (string field in fields) { if (dictionary.ContainsKey(field)) { //duplicate found! } else { int value = 0; //not used but required by Dictionary dictionary.Add(fieldvalue); } } But what I suggest you to use hash table where you can use the key-value pair to eliminate the duplicate e-mail address.