Traverse A List And Retrieve A Specified Value From List<> In .net/c#

I have a list which is defined as List<SoftwareTitles> softwareTitlesList = new List<SoftwareTitles>();

and the SoftwareTitles is a class which is defines as follows:

public class SoftwareTitles
{
string softwareTitle;
string invoiceNumber;[code]....

And now I'm adding the values from the sql server database to the list defines as follows:

public List<SoftwareTitles> SoftwareListRetrieve()
{
ConnectionToSql con1 = new ConnectionToSql();
string connectionString = con1.ConnectionStringMethod();[code]....

I want to find out the software title for every occurence of invoice number by looping through List<>. And I don't know how ? I have tried to loop through the List<> by the following code. I wanted to use something like contains i.e., softwareTitlesList[i].contains but seems like there is no such property or method

for(int i=0; i<softwareTitlesList.Count;i++)
{
softwareTitlesList[i].