Question

How can use projection to select with where clause specification?

Perhaps something like?:

List<string> Titles = 
  iEnumerableResultSet.Select(x => x.Title = "Whatever", x=> x.Id =5).ToList();

Answer 1

In my opinion, Select is poorly named. It is suppose to remind you of SELECT from SQL. That is, you specify the values that you want for each object in collection that you are Selecting over (if you know functional programming Select is the same as map).

To filter, what you want is Where:

var filteredResultSet = 
    iEnumerableResultSet
       .Where(x => x.Title == "Whatever" && x.Id == 5)
       .ToList();

How can use projection to select with where clause specification?

Now, your question seems to be asking how to both filter and project. You can say

var titles =
    iEnumerableResultSet
        .Where(x => x.Id == 5) // filter
        .Select(x => x.Title)  // project
        .ToList();  

You can think of this as being like the SQL query

SELECT Title
FROM SomeTable
WHERE Id = 5